High microwave power (1000W) Electron Cyclotron Resonance (ECR) Cl2/Ar plasma produce etch rates for In0.5Ga0.5P, Al0.5In0.5P and Al0.5Ga0.5P of ˜1um/min. at low pressure (1.5mTorr), moderate rf power levels (150W) and room temperature. Addition of Cl2 into Ar makes much smoother etched surface morphology as well as increasing the etch rate. All parameters, including microwave power, chamber pressure and rf power increase the etch rate of these alloys. Especially, there is at least a minimum rf power in order to get much higher etch rate with increasing microwave power. AlGaP in Cl2/Ar discharges has lower etch rates than InGaP or AlInP, which is similar to the results based on CH4/H2/Ar plasma chemistries. The Cl2/Ar chemistry enables smooth, high-rate etching without the need for polymer addition and thus simplifies the processing.

Etch rates up to 7,000Å/min. for GaN are obtained in Cl2/H2/Ar or BCl3/Ar ECR discharges at 1–3mTorr and moderate dc biases. Typical rates with HI/H2 are about a factor of three lower under the same conditions, while CH4/H2 produces maximum rates of only ˜2000Å/min. The role of additives such as SF6, N2, H2 or Ar to the basic chlorine, bromine, iodine or methane-hydrogen plasma chemistries are discussed. Their effect can be either chemical ( in forming volatile products with N) or physical ( in breaking bonds or enhancing desorption of the etch products). The nitrides differ from conventional III-V's in that bondbreaking to allow formation of the etch products is a critical factor. Threshold ion energies for the onset of etching of GaN, InGaN and InAlN are ≥75eV.

Electron Cyclotron Resonance (ECR) plasma etching with additional if-biasing produces etch rates ≥ 2,500Å/min for InGaP and AlInP in CH4/H2/Ar. These rates are an order of magnitude or much higher than for reactive ion etching conditions (RIE) carried out in the same reactor. N2 addition to CH4/H2/Ar can enhance the InGaP etch rates at low flow rates, while at higher concentrations it provides an etch-stop reaction. The InGaP and AtlnP etched under ECR conditions have somewhat rougher morphologies and different stoichiometries up to ˜200Å from the surface relative to the RIE samples.

InGaAs (C) grown by gas-source MBE is found to contain significant concentrations 5 × 1018 cm−3 of hydrogen that is incorporated from the source gases. Subsequent deposition of ECR-CVD SiNx films as surface encapsulation produces additional hydrogen incorporation from the SiD4/N2 precursors, but actually reactivates C acceptors that were passivated in the asgrown InGaAs. Further thermal treatments produce substantial hydrogen in-diffusion from the SiNx film into the InGaAs, causing changes in sheet resistance and contact resistance. These processes simulate several steps in the formation of the base mesa of an InGaAs-based heterojunction bipolar transistor, and show how subtle changes in the temperature of these processes can affect subsequently device performance and apparent reliability.

In this paper a study of the growth of GaAs and InP based materials using the alternative precursors TBAs and TBP is presented. For this purpose mass production multiple wafer reactors were employed. Both long-wavelength materials such as GaInAsP on IWP and short wavelegth like GaInP and AIGaInP on GaAs are investigated. The results demonstrate that ther is no loss of material quality when using these novel precursors. In all cases growth temperatures and V/III ratios could be significantly lowered.

structural, optical and electrical properties were evaluated. Significant progress has been made toward the growth of high performance HgCdTe devices by molecular beam epitaxy. Long wave infrared detectors operating at 9.9 μm at 78K exhibited a mean RoAo product of 1170 Ωcm2 at 0-fov. Very long wave infrared detectors operating at 14 μm at 78K exhibited a mean RoA product of 3.5 Ωcm2 at f/2 fov. These values represent the state-of-the- art for molecular beam epitaxially grown HgCdTe detectors.

We performed a polarization control method for vertical-cavity surface-emitting lasers by tilted-etching of the air-post. Circular laser posts were etched by tilting the substrate toward [110] or [110] direction with an angle of 15° ˜ 20° using reactive ion beam etching. For the laser devices with a diameter of 7 ˜ 10 μm, we observed outstanding selectivity of the polarization state. We found a dominant polarization perpendicular to the tilted direction. The maximum orthogonal polarization suppression ratio was about 25 dB. The selectivity of polarization in the tilted laser post devices is interpreted to be originated from the difference of optical losses of the two waves polarized to the [110] and [110] directions.

The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at ≥450°C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until >800°C, and its diffusivity is relatively high (˜10−11cm2/s) even at low temperatures (<200°C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30 - 40 meV. It is essentially immobile up to 1100°C. Carbon can produce low p-type levels (3×1017cm−3) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

A shift in the peak response wavelength and a broadening of the photoresponse spectrum is demonstrated for intersubband absorption in n-doped GaAs/AIGaAs multiple quantum well detectors following intermixing of the well and barrier layers during rapid thermal annealing. In general, a decrease in performance is observed for the RTA QWIPs when compared to the as-grown detectors. The peak absolute response of the annealed QWIPs is lower by almost a factor of four, which results in corresponding decrease in quantum efficiency. In addition, the noise performance results in a detectivity which is five times lower than that of QWIPs fabricated from as-grown structures.

Optical bandgap thermometry is a new method for measuring the temperature of semiconductor substrates. In this method, the temperature of the substrate is inferred from the wavelength of the onset of transparency of the substrate which is a measure of its bandgap. Common configurations of this technique are diffuse reflectance and transmittance. In order to calibrate these spectra to substrate temperature and to better understand the temperature dependence of the absorption edge, the transmittance spectra of semi-insulating InP:Fe and n-type InP:S substrates have been measured as a function of temperature in a tube. The width of the absorption edge (Urbach parameter) is found to increase linearly with temperature from 8.7 meV at room temperature to 15.7 meV at 595°C for semi-insulating InP:Fe while it remains independent of temperature at a value of about 21.5 meV for heavily doped (6.5×1018 cm−3) InP:S. For InP:Fe, the temperature dependent part of the width is smaller than predicted by the standard theory where the width of the edge is proportional to the phonon population. The values of the Urbach parameter for InP:Fe are higher than those of semi-insulating GaAs which is attributed to the higher ionicity of InP.

W, WSi0.44 and Ti/Al contacts were examined on n+ In0.65Ga0.35N, InN and In0.75Al0.25N. W was found to produce low specific contact resistance (Qc ˜ 10−7 Ω cm2) ohmic contacts to InGaN, with significant reaction between metal and semiconductor at 900 °C mainly due to out diffusion of In and N. WSix showed an as-deposited Qc of 4×10−7 Ω cm2 but this degraded significantly with subsequent annealing. Ti/Al contacts were stable to Ω 600 °C (Qc, ˜ 4×10−7 Ω cm2 at ≤600 °C). The surfaces of these contacts remain smooth to 800 °C for W and WSix and 650 °C for Ti/Al. InN contacted with W and Ti/Al produced ohmic contacts with Qc ˜ 10−7 Ω cm2 and for WSix Qc ˜ Ω cm2.All remained smooth to ˜ 600 °C, but exhibited significant interdiffusion of In, N, W and Ti respectively at higher temperatures. The contact resistances for all three metallization schemes were ≥ 10−4 Ω.cm2 on InAIN, and degrades with subsequent annealing. The Ti/Al was found to react with the InA1N above 400 °C, causing the contact resistance to increase rapidly. W and WSix proved to be more stable with Qc ˜ 10−2 and 10−3 Ω cm2 up to 650 °C and 700 °C respectively.

Transmission electron microscopy has been applied to study the ordering in size and shape of InAs quantum dots and in their lateral distribution. InAs islands were grown by MBE on GaAs substrates at different As-pressures and growth temperatures. Experiments with growth interupption support the theoretical predictions concerning equilibrium island size, shape and arrangement. The stability of the equilibrium dot arrays to changing of growth conditions was studied by varying the deposition temperature, arsenic pressure or growth interruption time. Significant deviation from the optimal As-pressure towards both the lower and higher values was shown to supress the formation of InAs dots resulting either in mesoscopic InAs clusters or 2D corrugated islands. Energy benefit due to the strain relaxation at island edges explains the experimental results better than kinetic consideration.

GaN films and ZnO buffer layers have been deposited on c-cut sapphire substrates by pulsed laser deposition (PLD) employing a KrF laser (λ = 248 nm). The influence of the deposition parameters, such as substrate temperature and gas pressure during growth, have been studied. GaN films grown above 700 °C are single crystalline and the full width of half-maximum (FWHM) of the GaN (0002) peak decreases to 0.37° as the growth temperature increases to 800 °C. The optimum growth pressure for GaN is determined to be 0.01 torr N2. The optical transmission below the bandgap of the GaN film grown at this pressure is over 85%.

We propose a novel superlattice (SL) InAsySb1−y)/InxTl1−xSb lattice matched to InSb for a potential application as an infrared detector material in the 8–12 μm wavelength range. We report on the results of energy band calculations for this SL using the modified Kronig-Penney model. Our preliminary calculations indicate that InAs0.07Sb0.93/In0.93Tl0.07Sb would exhibit a type-I SL with conduction band offset of 34 meV and valence band offset of 53 meV at 0K. Due to the lack of accurate information on material parameters, namely, energy offsets and effective masses of InTlSb, these were estimated by comparison with the behavior of HgCdTe system. The theory predicts three heavy hole subbands and one partially confined electron in the 30Å InAs0.07Sb0.93/100Å In0.93Tl0.07Sb SL. The band gap of the SL was computed to be 0.127 eV (9.7 μm). It is expected that this SL will allow improvements in the InTlSb epilayers’ structural quality as it will be sandwiched between higher quality zincblende InAsSb layers.

Surface passivation is a key issue in compound semiconductor device technology. The high density of surface states on unpassivated surfaces can lead to excessive non-radiative recombination at the surface, affecting optical devices, or provide leakage and low-field breakdown in electronic devices. Our previous studies on low energy, low-dose hydrogen ion treatment carried out at room temperature showed long-term improvement in the optical properties of near surface quantum wells. We have accordingly applied this process to GaAs-based pseudomorphic HEMTs (PHEMT) in order to improve their power performance. Although our process is designed so that the hydrogen reactions are confined to the surface of the substrate, a critical factor in the success of this treatment is the extent of in-diffusion of the hydrogen, and the possibility of dopant passivation. PHEMT structures were hydrogenated at various conditions and both Hall mobility and carrier density were monitored. For a low hydrogen ion dose (3 × 1016 cm−2) at 80 eV energy, some degradation of Hall mobility and carrier density was noted after the treatment, but full recovery of both parameters was achieved after a 400°C thermal anneal. Much higher hydrogen doses resulted in severe degradation of mobility and carrier density, which were only partially recovered after thermal anneal. Measurements on actual PHEMT devices showed an approximately 15% decrease in the transconductance, and in addition, a 60% decrease in the gate-to-drain leakage current after irradiation with 80 eV hydrogen ions at a dose of 3 × 1016 cm−2. The decrease of the leakage current indicates that passivation is taking place. The decrease of the transconductance suggests that hydrogen may be diffusing into the regions of the dopants. Optimization of the hydrogenation parameters should allow leakage reduction without sacrifice of transconductance.

We summarize the characteristic defect structures associated with gradual-degradation, rapiddegradation, catastrophic (mirror-facet) optical damage (COD), electric static discharge (ESD) and electric overstress (EOS) damages to provide a defect-map for device failure mode analysis. The generation mechanisms of these lattice defects are discussed which pinpoint the weak links in the device structures.

Threshold current density in GaN-based UV double-heterostructure lasers is predicted in the range of 2- 4 kA/cm2 using theoretical calculation of optimized heterostructure for various types of devices. Freecarrier (FC) and Coulomb-enhancement (CE) models are compared. Results are given for different combinations of effective masses. The minimum threshold current is not strongly influenced by the choice of effective masses. The FC model predicts lower than CE threshold in edge-emitting lasers, whereas the CE model predicts lower than EC threshold in thin VCSEL devices.

The temperature dependence of the Hall voltage and resistivity of highly carbon doped GaN were measured. From the sign of the Hall voltage, the material appears to be p-type. Charge transport takes place in an impurity band and the valence band. The effective activation energy as estimated from the maximum in the temperature versus Hall voltage relation is 10–30 meV.

Inductively Coupled Plasma (ICP) sources are extremely promising for large-area, highion density etching or deposition processes. In this review we compare results for GaAs and GaN etching with both ICP and Electron Cyclotron Resonance (ECR) sources on the same singlewafer platform. The ICP is shown to be capable of very high rates with excellent anisotropy for fabrication of GaAs vias or deep mesas in GaAs or GaN waveguide structures.