Previous studies have helped elucidate the underlying mechanisms for selective area epitaxy in chemical beam epitaxy by investigating the reactions of triethylgallium (TEG) on a silicon nitride surface. However no explanation was produced as to why selective growth is lost at low temperatures or high Gp V beam fluxes. This question is addressed in this paper which examines the interaction between TEG and As2 on the silicon nitridesurface. In the absence of arsenic, TEG adsorbs with a low sticking probability on the dielectric. Adsorbed species mainly desorb rather than decompose, and any Ga produced on the surface becomes converted to a nitride form; no free Ga is produced hence GaAs growth cannot occur. Arsenic is found to form a weakly adsorbed phase on the nitride surface. Reaction with co-adsorbed TEG results in the formation of GaAs. Adsorbed As also is efficient in increasing the reactive sticking probability of TEG.The results provide further insight into the reaction mechanisms governing selected area epitaxy.

In metal organic chemical vapor deposition (MOCVD), the most commonly used sources are the trimethyls of Al, Ga, In, and Sb, and PH3 and ASH3. New organometallic sources are being developed as the understanding of the deposition process improvesand allows for the determination of the effects of source type and growth condition on the properties of the grown films. These new sources are safer and allow for the growth of higher purity materials using more favorable growth conditions. InSb and AlSb prepared using these trimethyl-sources are not of high enough quality to be used in many current device applications. Alternate organometallic Sb sources are being investigated to improve the materials characteristics of InSb grown by MOCVD.InSb grown using trimethylindium (TMIn) and trimethylantimony (TMSb) or triethylantimony (TESb) yielded similar quality materials under similar growth conditions. InSb grown using triethylindium (TEIn) and TESb under similar growth conditions yielded very poor quality n-type material. Three new organometallic Sb sources, triisopropylantimony (TIPSb), tris(dimethylamino)antimony (TDMASb), and tertiarybutyldimethylantimony (TBDMSb) are being investigated. The growth of InSb using TIPSb, TDMASb, or TBDMSb and TMIn was investigated over a temperature range of 350 to 475 °C. InSb grown from TDMASb had similar properties to InSb grown from TMIn and TMSbwhen using a similar temperature and V/III ratio range. The growth rates of InSb using TMIn and either TIPSb or TBDMSb at temperatures <= 425 °C were proportional to both the TMIn flow rate and the temperature. The surface morphology of InSb grown using eitherTIPSb or TBDMSb was very rough for growth temperatures <=425 °C. This may be due to the complex decomposition mechanisms involved and the presence of methyl groups on the surface. The InSb with the highest mobility was grown at 400 °C and a V/III ratioof 3 using TIPSb. It was n-type with a carrier concentration of 2.5 × 1015 cm−3 and a mobility of 78,160 cm2/Vs at 77 K. Both n- and p-type InSb were grown using TBDMSb with mobilities up to 67,530 and 7773 cm2/Vs, respectively at 77 K. The mobility for InSb using either TIPSb or TBDMSb was optimized by going to lower temperatures, pressures and V/III ratios. The opposite was truefor surface morphology which improved with higher temperature, pressure, and V/III ratio. The growth of high mobility InSb with smooth surfaces at T<=425 °C was not achieved with TIPSb or TBDMSb and TMIn under the conditions investigated in this work.

Triethylgallium, trimethylindium and tertiarybutylarsine have been used to grow GaAs and InGaAs on (OO1)GaAs. No pre-cracking was used so that the thermal decomposition of tertiarybutylarsine on GaAs could be studied. The growth has been monitored in-situ using reflection high-energy electron diffraction and reflectance-difference. A comparison ismade between the reflectance difference signal and the intensity of the reflection high-energy electron diffraction specular spot as the surface is transformed from As rich to Garich. Using the former technique similar growth transients have also been studied as a function of the temperature. It is found that the incorporation of small amounts of In (less than 5 per cent) in the buffer layer significantly improves the oscillatory behavior of the RD-signal when growth of GaAs is commenced. Finally, the growth dynamics of InGaAs isstudied using reflection high-energy electron diffraction.

The adsorption and decomposition of GaH3NMe3 and GaH3PMe3 on GaAs (100) has been investigated using XPS, TDS and molecular beam techniques. Both precursors react in a similar way with the adsorbed layer formed at low temperatures decomposing as the temperature is raised to produce metallic Ga, gaseous gallium hydride(s) and adsorbed hydrogen and the Lewis base, which also undergo desorption. Molecular beam measurements show that both compounds exhibit similar decomposition kinetics and decompose more readily than the aluminium analogues. The results indicate that the site-blocking effects, which prevent the low temperature decomposition of alane adducts, are less significant for the gallane compounds.

Carbon-doped base InGaP/GaAs single and double heterojunction bipolar transistors (HBTs) grown by gas-source Metal Organic Molecular Beam Epitaxy (MOMBE) are reported. Large are devices (emitter diameter 70 μm) exhibited gain of 25 for high injection levels at a base doping of 5 × 1019 cm−3. Ideality factors (<1.1)were obtained for both emitter-base and base-collector junctions in both single (SHBT) and double PHBT) heterojunction devices. Vceo's of 12 V and 19 V for SHBTs and DHBTs respectively were measured.

Excimer laser light has been used to achieve the maximum growth rate of GaAs in a chemical beam epitaxy system when temperatures were more than a hundred degrees below the normalgrowth temperature. Secondary electron and transmitted electron microscopy of material grown using laser assistance shows the presence of surface ripples aligned with crystallographic directions. Layers grown at the lowest temperatures using a high fluence of excimer laser light contain a high density of small dislocation tangles (>1011 cm-−2 ). Lower fluences have no effect on the microstructure of the material.

Two metallorganic phosphorous precursors, bisphosphinoethane (BPE) and tertiarybutyl phosphine (TBP), were studied. For indium phosphide (InP) grown using BPE, the measured room temperature and 77K Hall mobilities were 4,200 and 22,000 cm2/Vs, with carrierdensities 5.7E15 and 4.0E15 cm−3, respectively. For InP grown using TBP, the measured room temperature and 77K Hall mobilities were 4,400 and 26,000 cm2/Vs, with carrier densities 6.4E15 and 5.1E15 cm−3, respectively. An impurity build-up at the substrate interface is responsible for the relatively low mobility in the adjacent epitaxial layers. SIMS analysis showed that S and Si are the primary impurities measured in films grown with BPE and TBP, respectively; impurity concentrations increasedwith cracking temperature. The full width at half maximum (FWHM) of donor bound exciton peaks measured by 2.2K photoluminescence for InP grown by BPE and TBP were 0.84 and 1.28 meV, respectively.

In this paper we report the growth of GaP/Si heterostructures by metalorganic chemical beam epitaxy (MOCBE), including information on a MOCBE system custom built for this work. The gallium source was triethylgallium and the phosphorus source was tertiarybutylphosphine. The range for GaP epitaxy is 260 <T< 375°C. Methods of characterization included scanning electron microscopy (SEM), Auger electron (AES), X-ray photoelectron (XPS) and Rutherford backscattering (RBS) spectroscopies.

We have used x-ray photoelectron spectroscopy, temperature programmed desorption, and epitaxial growth experiments to study the feasibility of using divinylmercury (DVHg) as a precursor for metalorganic molecular beam epitaxial (MOMBE) growth of Hg-containing II-VI materials. The surface chemistry associated with the interaction of DVHg and Te was investigated using polycrystalline Te (poly-Te) films as the substrates for DVHg adsorption. nDVHg dissociatively adsorbed on a poly-Te surface at temperatures as low as -118°C. However, the DVHg dissociation probability was temperature dependent and substantially less than unity when extrapolated to typical Hg1−xCdx Te growth temperatures of 150–200°C. Preliminary results from MOMBE growth experiments showed that successful MOMBE growth of HgTe on CdTe//ZnTe//GaAs using DVHg and thermally precracked diethyltellurium was only possible when the DVHg was also thermally precracked. Simultaneous exposure of atomic H and DVHg to a poly-Te surface significantly enhanced the dissociative adsorption of DVHg, indicating that the presence of atomic H in the growth environment may be an effective alternative to precracking DVHg for MOMBE growth.

Compounds of the general forms Zn[N(R)2]2, Zn(N(R)(R')2] and Zn{[N(R)2][N(R')2]} have been prepared, these new compositions have been characterized by multinuclear NMR, GC/MS, FTIR, elemental analysis and single crystal x-ray diffraction, and they have been evaluated for their potentialto serve as “designer dopants” in the epitaxial growth of p-type ZnSe. Retention of the Zn-N bond during deposition should insure selective location of the nitrogen atom on the native selenium lattice site. Precursor vapor pressures, vapor phase decomposition mechanisms, and thin film properties are presented. Results from materials characterization by XRD, SIMS, PL, Raman and SEM are presented in the context of evaluating dopantlevel.

The thermal behaviour of dialkylindium-dialkylamides R2InNR/2 (R,R'=Me, Et) and dialkylindium-azolides R2lnNR' (NR'=Pyrrole, Pyrazole) has been examined by a mass spectrometric thermal evolution technique, in the temperature range 30–400°C. Data on volatility, identity of gasified molecules, threshold temperature and products of the decomposition processes are reported and discussed.

Doping of GaAs with dimethylaluminum methoxide and its effects have been studied during metalorganic vapor phase epitaxy. Oxygen concentration decreases exponentially with increasing growth temperature and the activation energy equal to 1.8 eV.Increase of oxygen content with decrease of V/III ratio indicates that oxygen most likely occupies arsenic site. Photoluminescence intensity was observed to decrease with increasing oxygen contentand three new deep level luminescence peaks appeared at 75, 96, and 160 meV below the band gap. This, together with the fact that as-grown layers are fully depleted, indicates that oxygen is electrically active in OMVPE GaAs and forms deep non-radiative recombinationcenters.

The novel antimony source compound di-isopropylantimony hydride, (i-Pr)2 was synthesized and evaluated for use as a volatile Sb-source compound for low temperature growth of Sb-containing semiconductor materials. (i-Pr)2SbH was pyrolyzed in a horizontal atmospheric pressure organometallic vapor phase epitaxy (OMVPE) reactor using Arand H2 as carrier gases. The gaseous exhaust products were analyzed by a residual gas analyzer. Complete pyrolysis of (i-Pr)2SbH in our OMVPE reactor occursaround 300°C and 350°C in Ar and H2, respectively. A comparison between the pyrolysis temperatures and pyrolysis byproducts with respect to a proposed decomposition mechanism of (i-Pr)2SbH is presented. Sb films were grown on Si(100) andSi(111) as low as 200° C. The Sb films were analyzed by Auger and X-ray diffraction. These polycrystalline Sb films were free of detectable carbon by AES. X-ray diffraction data indicated that these Sb films were highly oriented in the [000L] direction.

New dialkylgallium dialkylphosphide compounds having the formula [(t- Bu)(R)GaPR'2]n (R = t-Bu, Me3SiC=C; R' = t-Bu, i-Pr, Et; n = 1, 2) were recently prepared and characterized. When R = R' = t-Bu, the compound is a low melting, monomeric solid. The other compounds are dimeric solids with the unsym-metrical acetylides occurring as cis and trans isomers. Polycrystalline gallium phosphide was deposited from these sources on silicon atlow pressure (0.05–0.1 Torr) and low temperature (350–600 °C) in a horizontal OMVPE reactor. The film growth was monitored by a residual gas analyzer and the by-products were trapped (N2(1)) to be later analyzed by 1H and 13C NMR. The deposited films were characterized by Raman spectroscopy, X-ray powder diffraction, and Auger emission spectroscopy.

Tertiarybutylarsine (TBAs), tris-dimethylaminoarsenic (DMAA), and tertiarybutylphosphine (TBP) were investigated as alternatives to arsine and phosphine for the growth of AlGaAs, AlInAs, and AlInP by organometallic vapor phase epitaxy. The use of TBAs led to a significant reduction in carbon and oxygen incorporation compared to ASH3 for AlGaAs. Increasing the TBAs molar flow rate reduced the oxygen (and carbon) concentration. Lower oxygen concentration was observed in AllnP grown with TBP compared to PH3. Increasing the PH3 molar flow rate decreased the oxygen incorporation in AllnP. The morphology of AllnP improved considerably as the growth temperature was increased from 650°C to 750°C, similar to the case of PH3. AlInAs and AlGaAs layers grown with DMAA exhibited rough morphology, presumably due to oxygen-containing impurities in the DMAA source.

Reaction and transport models describing the deposition of thin films of ternary compoundsemiconductors by Metalorganic Vapor Phase Epitaxy (MOVPE) are being developed. The growth of AlxGa1−x As (0≤x≤1) films from trimethyl-aluminum (TMA1), trimethyl-gallium (TMG) and arsine has been used as a typical example. A kinetic model of the process including both gas phase and surface reactions has been coupled to a two-dimensional transport model of a horizontal reactor with a flat susceptor. The model predicts reported experimental observations on growth rates and film compositions [1] using a single adjustable parameter, the activation energy of the the AlAs growth reaction. A parametric study was performed to identify operating conditions maximizing the thickness andcompositional uniformity of the deposited films. All inlet flow rates considered in this work were higher than the ones required to suppress transverse buoyancy-driven recirculations in the reactor [2,3]. Such conditions permit the growth of abrupt heterojunctions byrapidly switching various precursors on and off. Our results indicate that the most promising operating conditions coincide with the transition from kinetic limited to diffusion limited growth, which occurs at temperatures between 800 K and 850 K for typical experiments [1]. The optimal inlet mole fraction of the limiting group-III species was found to be about 6×10−4 for such cases.

Chemical sulfur treatments of GaAs have been shown to improve the GaAs surface electronic properties. These treatments result in lower surface state density, lower surface recombination velocity, and shifting or unpinning of the Fermi level, in addition to improvement in the performance of devices. However, there is still considerable controversy regarding the chemical nature of the surface film which results from this chemical sulfidation. It has been shown that this film is not stable chemically and electronically. The improved surface electronic properties decay with time and are sensitive to the chemical environment of the material. In this study, using surface infrared reflection spectroscopy (SIRS) and x-ray photoelectron spectroscopy (XPS), we have investigated the electrochemical sulfidation of GaAs as a possible new method to produce a GaAs surface that is stable chemically and electronically. We have found that anodic treatments with Na2S and (NH4S solutions result in the removal of the pre-existing oxide of GaAs and the formation of films comprising sulfur, sodium carbonate, ammonium thiosulfate, and sulfide and sulfur-oxygen compounds of arsenic. Rinsing the GaAs with water removes the bulk of the film, leaving behind a surface on which only arsenic sulfide was detected.

A two order-of-magnitude enhancement of photoluminescence intensity relative to untreated GaAs has been observed for GaAs surfaces coated with chemical vapor-deposited GaS. The increase in photoluminescence intensity can be viewed as an effective reduction in surface recombination velocity and/or band bending. The gallium cluster [(t-Bu)GaS]4 was used as a single-source precursor for the deposition of GaS thin films. The cubane core of the structurally-characterized precursor is retained in the deposited film producing a cubic phase. Furthermore, a near-epitaxial growth is observed for the GaS passivating layer. Films were characterized by transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectron and Rutherford backscattering spectroscopies.

The interaction of semiconductor surfaces with aqueous acid solutions is important in chemical cleaning and etching. Wet chemical treatments are advantageous because they cause little damage to the surface and do not usually require high temperatures. The surface chemistry of GaAs after treatment with phosphoric acid was studied using multiple internal reflection infrared spectroscopy. The treatment left behind a thin film containing several types of PxOy bonds. The chemical nature of the film was observed to change with time as new species would form on the surface.

A comparison is given of the dry etching characteristics of InP and related materials in high ion density (>1011 cm−2 ) microwave discharges of HI, CH3I, C2H5I, C3H7I and C2H3I. The InIx species are more volatile than their InClx counterparts near room temperature and rapid etch rates can therefore be achieved without the need for sample heating. HI discharges provide faster etch rates than the halocarbon-based mixtures, but are more corrosive. All of these gas chemistries offer faster rates than conventional CH4/H2 mixtures. Halocarbon-iodide discharges still suffer from polymer deposition on the mask and within the reactor, as with CH4/H2. AES analysis shows an absence of contaminating residues with all of the iodine-based chemistries, and highly anisotropic features are obtained since the etching is driven by ion-enhanced desorption of the reaction products.