Magnetron dry etching using SiCl4, combined with a smooth reflowed photoresist masking technique has been used to fabricate GaAs/AlGaAs ridge waveguides. The effect of pressure, flowrate and power on etch rate and sidewall smoothness has been studied. Waveguides fabricated using optimum parameters exhibited optical losses lower than those achievable using wet etching. This process was further used in the fabrication of Fabry Perot ridge lasers, detectors and phase modulators.

Silicon oxynitrides with compositions varying from Si3N4 to SiO2 were deposited on silicon substrates by electron cyclotron resonance plasma enhanced chemical vapour deposition (ECRPECVD). The silicon source used is an organic liquid, Tris Dimethyl Amino Silane (trade name SiN – 1000TM). Optical emission spectroscopy is used to characterize the ECR plasma, this information then is correlated with the optical properties of the deposited film, as determined by in situ ellipsometry. Auger electron spectroscopy showed that only low levels of carbon (< 3 at%) are present. The SiO2 and Si3N4 films are close to stoichiometric, with low levels of bonded hydrogen as determined by infrared absorption spectroscopy.

Planar waveguide structures were fabricated and tested using the prism coupling technique to determine the mode effective indices. These are compared to those expected from the ellipsometry measurements.

We describe an in-situ fabrication process which combines electron cyclotron resonance (ECR) plasma H2 to clean native oxides, ECR SiCl4 to etch anisotropically, a brief Cl2 chemical etch to remove any near surface damage and contamination, and molecular beam epitaxial (MBE) regrowth. We report the first buried heterostructure (BH) AlGaAs/GaAs/InGaAs edge emitting laser diodes fabricated using this in-situ process. The lasers operate in continuous mode without noticeable degradation.

The effect of CH4/H2 reactive ion etching (RIE) on Si-doped AlxGa1−xAs (x=0.25) is studied by deep level transient spectroscopy (DLTS) and Hall measurements. After RIE exposure, the samples were annealed between 250 and 500°C in order to study the recovery kinetics of deep and shallow levels. Non-etched reference samples showed broad DLTS spectra which were deconvoluted in two different emission peaks. We assigned them to DX1 and DX2 centers. The different deep levels are characierized by different aluminium configurations, one or two aluminium atoms, surrounding the silicon donor which are responsible for the DX centers. After RIE exposure and subsequent thermal annealing, a third emission peak is observed. This emission is attributed to the DX3 center, which is characterized by three aluminium atoms neighbouring the silicon donor. The recovery activation energy is calculated based on first-order kinetics. The activation energies are found to be around 1.9 eV in all cases.

Complementary Hall measurements as a function of temperature (4-300 K) were used to characterize the electron capture of deep levels in Si-doped AlGaAs exposed to CH4/H2 RIE. We observed that the samples exposed to RIE and annealed at temperatures higher than 400°C exhibit electron capture in the 120-150 K temperature range. On the other hand, samples annealed at lower temperatures, showed additional capture features between 200 and 230 K.

We have extended the capability and versatility of a chemical beam epitaxial (CBE) system by demonstrating reactive chemical beam etching (RCBE) of InP using phosphorus tri chloride (PCl3)as the gaseous etching beam injected directly into the growth chamber. This permits instant switching from etching to growth (and vice versa) in the same run for the first time in CBE. We investigated RCBE of InP at various substrate temperatures between 400 °C and 580°C, under different PCl3 fluences, and etching conditions. Excellent surface morphology was obtained at high temperatures (> 530°C - 570°C) and under an etching rate of < 6 Å/sec. We also found that upon addition of trimethylindium flow equivalent to a growth rate of 1 Å/sec during RCBE a dramatic improvement in surface morphology was obtained even at a high net etching rate of 10 Å/sec. The surface morphology obtained under such conditions is indistinguishable from that of the original substrate surface. Using Si02 as a mask, in-situ etching of laser mesas followed immediately by regrowth of blocking layers with excellent wetting characteristics was obtained.

The damage introduced by CH4/H2 reactive ion etching (RIE) on Si-doped AlGaAs layers is studied by X-Ray Photoelectron Spectroscopy (XPS), Auger electron spectrocopy (AES) and electrical measurements on Schottky contacts. The XPS analysis of the surface stoichiometry after RIE exposure shows arsenic depletion and adsorbed carbon as the main characteristics. The carbon spectrum consists of a component due to atmospheric contamination and an additional photoelectron peak at 283 eV, which we correlate with the formation of Ga-C radicals at the AlGaAs surface during RIE. The reaction process at the Au/TiW/Ti/AlGaAs interface after RIE exposure and subsequent thermal annealing is monitored by AES. Also by this technique, carbon was detected at the Ti/AlGaAs interface and no interdiffusion was observed. The electrical behaviour of the contacts is characterized by capacitance-voltage (CV) and current-voltage (IV) measurements. Schottky barrier height, ideality factor and reverse breakdown were determined. The barrier height extracted from CV measurements of the samples exposed to RIE shows increased values (1.1 to 1.4 eV) compared to the reference samples (1.0 to 1.1 eV), depending on the aluminium concentration. The same behaviour was observed in the ideality factor. The results are explained by the formation of a p-n junction below the metal/AlGaAs barrier. Good agreement between experimental and theoretical values is found when the compensation of Si donors was taken into account.

The formation of ohmic contacts to p-GaAs based on Au-Zn system comprising a TiN diffusion barrier has been investigated using 2 MeV He+ RBS and the specific contact resistance measurements. It has been proved that TiN films deposited by reactive RF bias magnetron sputtering serves two purposes. First it suppresses the arsenic evaporation and thus confines the reaction between AuZn and GaAs. Second, it prevents intermixing between p-GaAs/Au(Zn) ohmic contact and an overlayer of Au.

Multilayer metallizations of Pd/Ge/Pd, with different thickness ratios of Ge and Pd, were deposited onto n-type InP by means of electron beam evaporation. The specimens were then annealed in flowing N2 gas at temperatures ranging from 250 to 425°C for various times. Transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX) and electron diffraction were used to identify the phase changes during reaction. The four point probe method was used for electrical resistance measurements. A Pd-In-P amorphous phase and a Pd2Ge compound formed during deposition. Subsequent annealing resulted in crystallization of the amorphous phase followed by epitaxial growth of Pd2InP(II) on InP at 350°C. At 425°C, Pd2InP(II) with Ge in solution, decomposed producing a contact with a lower specific contact resistance. The lowest contact resistances achieved were ∼10−5 Ωcm2. Further annealing led to more decomposition of InP, including presumably the Ge doped InP surface region, which corresponded to an increase in contact resistance.

The surface of InGaAs (In 53 %) lattice-matched to InP has been phosphidized using phosphine plasma. X-ray photoelectron spectroscopy analysis indicates that substitution of phosphorus for arsenic and deposition of phosphorus layer occur due to phosphidization. Formation of indium and arsenic oxides is suppressed at the phosphidized surface of InGaAs, while phosphorus oxide is observed. Tunneling metal-insulator-semiconductor type Schottky contacts are formed on phosphidized InGaAs by evaporating various metals such as Au, Cu, Ti and Al. An effective barrier height as high as 0.7 eV is evaluated from the room temperature current-voltage characteristic for Au/InGaAs Schottky contacts. The true barrier height estimated from the Richardson plot varies depending on the metal work function.

The reactions between (100) GaAs and Au, Zn, and Au(Zn) ohmic contact metallization have been investigated by the use of transmission electron microscopy and x-ray diffraction. Emphasis is placed on the particular role of Zn during consecutive stages of the formation of an ohmic contact to p-GaAs. The most significant feature of the interaction of Zn with GaAs is the penetration of Zn atoms into the native oxide, which remains at the surface of GaAs after chemical treatment. Moreover, the presence of Zn in Au-based metallization is found to considerably suppress the thermally induced growth of metallization grains, making the microstructure of the contact virtually intact upon annealing at temperatures up to 460°C.

Obtaining good p-ohmics to the base layers of AlGaAs/GaAs HBTs have been difficult due to metal spiking and instability of the contacts to subsequent processing temperatures. To avoid spiking, non-alloyed contacts have been traditionally used. In this paper, we present a stable, non-spiking, low contact resistivity alloyed p-ohmic contact to HBT structures.

The limiting transport processes for current flow across metal-semiconductor (MS) ohmic contacts to n- and p-type InP have been investigated for Au-based metallizations containing the doping elements Germanium and Zinc. It has been found that the Schottky barrier is lowered and in some cases vanishes during annealing. The current flow for an optimal ohmic contact is diffusion limited by a Fermi potential difference between the alloyed metallization and the bulk InP. For non-optimal ohmic contacts the current flow is also limited by thermionic emission across a low effective Schottky barrier.

A Pt/Ge/Au contact of the structure: <n-GaAs>/Pt(17nm)/Ge(25nm)/Au(43nm), overlaid with a Ta-Si-N barrier layer and a Au metallization layer has a contact resistivity, ρc, of 3.7×10−6 Ωcm2 after annealing at 450°C for 15 min. After aging at 450°C for 60 h, ρc slightly degrades to 5.5×10−6 Ωcm2 while the surface keeps smooth. When alloyed at 550°C for 15 min, ρc is 1.8×10−6 Ωcm2 and stays about the same value after annealing at 550°C for 1 h. Without the Ta-Si-N barrier and the Au overlayer, the Pt/Ge/Au contact alone is also ohmic after annealing at 450°C for 15 min but with a ρc of ∼10−5 Ωcm2 while the surface morphology deteriorates significantly after aging at 450°C for 20 h.

The thermal reactions of this Pt/Ge/Au contact on GaAs, with or without a Ta-Si-N barrier layer, are investigated by backscattering spectrometry, x-ray diffraction, and transmission electron microscopy in conjunction with energy dispersive analyses of x-rays. For all samples, the main reaction products after annealing at 450°C for 15 min are Au7Ga2, and PtGe:As, a PtGe phase that also contains arsenic. The product phases are randomly distributed within a laterally uniform reacted layer when the Pt/Ge/Au contact is covered by a Ta-Si-N layer. Without the Ta-Si-N barrier layer, a small arsenic loss and a Ga-rich phase (probably Gaoxides) on the contact surface are observed after annealing at 450°C. In this case, the surface and contact-semiconductor interface are more faceted than with a Ta-Si-N barrier layer.

The growth sequence of Al, Ge, and Ni metals has been shown to dramatically affect the amount of heat treatment time required to convert the ohmic contact metallization from Schottky to ohmic behavior. Interpretation of interdiffusion and phase formation of the Al-Ge, Al-Ni, or Ni-Ge thin film couples were measured. Auger depth profiles and thin film X-ray diffraction were used to determine interdiffusion and phase formation resulting from various types of thermal processing. The effects of interdiffusion and formation of phases such as Ni-Ga, Ni-As, Ni-Ga-Ge, and Ni-As-Ge from the two element metallizations on GaAs will be used to explain the origin of ohmic behavior for the ternary Al-Ge-Ni contacts to GaAs.

The author did experiments on ohmic contacts between alloyed goldgerumanium (AuGe) thin film systems and Si–implanted n–type GaAs crystal conductive layers on semi–insulating wafers in order to obtain stable ohmic contacts for source–drain electrodes of Si–implanted metal–semiconductor field–effect–transistor arrays as the tools of investigating semi-insulating GaAs crystallographic–characteristics uniformity. Hot–stage–alloyed low–Ge–content (content in charged AuGe wire: < a few wt.%) AuGe/Au films and GaAs crystal n–type Si–implanted layers showed smooth metallic surface morphology (like gold reflection) and low specific ohmic resistivity (≃10exp.−6 Ω/cm2) (by G.S.Marlow and M.B.Mukunda method) at Room temperature on the condition of typical 0.25 X 10exp.13/cm2− 1 X 10exp.13/cm2 Si dosage at 100keV–200keV and 850°C-15 min capless annealing in 2.7 Torr AsH3+Ar atmosphere for S.I GaAs crystal wafers.

This paper presents an experimental study of the physical and electrical characteristics of tungsten (W) thin films versus the deposition parameters of sputtering. A correlation between the W film characteristics and thermal stability of the W/GaAs Schottky diodes is also presented. Good thermal stability was obtained for W gates with low resistivity and α-W phase, deposited at low pressure and low RF power. W films deposited at high pressure presented high resistivity, β-W phase and weak thermal stability. Diodes annealed under As over-pressure ambient presented an enhanced thermal stability of about 100°C.

The first study of the TiW nitrides (TiWNx) as the Schottky contact metals to the n type Ga0.51In0 49P has been made. The Ga0.51 In0.49P epitaxial layer was successfully grown on the GaAs substrate by LP-MOCVD to form a lattice-matched heterostructure. The RF-magnetron sputtering system was utilized for the nitride deposition. The thermal stability of the nitride films were studied using rapid thermal annealing (RTA) method. Both the electrical characteristics and the materials characteristics were investigated. The materials properties of the nitride films were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). The TiWNx Schottky contacts demonstrate excellent electrical and physical characteristics, even after high temperature annealing. The barrier heights range from 0.81 to 1.05 eV depending on the content of the nitrogen and the annealing conditions. The XRD and AES results show no indication of interaction at the TiWNX/GaInP interface of both as-deposited and annealed samples. The outstanding characteristics of the contact were attributed to the high bandgap nature of the Ga0.51In0.49P and the incorporation of nitrogen into the TiW films.

Gold-based contacts on GaAs, i.e., Au(Te)/n-GaAs, Au(Ge)/n-GaAs, and Au(Zn)/p- GaAs, were annealed with or without an Al2O3 cap, in order to examine the effects of capping on their metallurgical and electrical properties. Current-voltage measurements showed that ohmic contact can be formed for all the metallizations, except capped Au(Te) which remained nonohmic even after annealing up to 480°C. Transmission electron microscopy and x-ray diffraction observations showed that the reactions between a contact and GaAs can be strongly affected by a capping layer. For all uncapped contacts, annealing generally resulted in growth of Au-Ga compounds and nonuniform contact morphology, whereas capped Au(Ge) and Au(Zn) contacts were stable and retained flat interface with GaAs. Capped Au(Te) was found to be unstable, reacting extensively with GaAs, due to the presence of Te. Electrical data are explained in terms of the doping model for ohmic contact formation.

It was observed that thin metal (catalytic metal: platinum) penetrated into a interface between a chemical vapor deposition (CVD) silicon dioxide film and a Si–implanted electric thermal furnace, on the way to carrying out experiments on alloyed ohmic–metals with Si–implanted electrically conductive n–type GaAs crystal layers in order to obtain stable and uniform ohmic contact electrodes of low specific ohmic contact resistances for metal–semiconductor field–effect–transistor arrays as a observation tool of semi–insulating GaAs–crystal crystallographic uniformity.

The damage production in GaAs, InAs, GaP and InP implanted with different mass ions in the temperature region 80K to 450K has been investigated by means of the RBS/channeling technique at 300K and 100K as well as by optical transmission and reflection measurements. The influence of the implantation parameters on the damage production as well as the differences observed for the various materials are discussed. Further, results concerning the electrical activation after rapid thermal annealing of GaAs and InP implanted at different temperatures are presented.