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The finite difference method was used to analyze the thermal characteristics of continuous wave 850 nm AlGaAs/GaAs implant-apertured vertical-cavity surface-emitting lasers (VCSELs). A novel flip-chip design was used to enhance the heat dissipation. The temperature rise in the active can be maintained below 40 °C at 4 mW output power with 10 mA current bias. By contrast, the temperature rise reaches above 60 °C without flip-chip bonding. The transient temperature during turn-on of a VCSEL was also investigated. The time needed for the device to reach the steady-state temperature was in the range of a few tenths of a millisecond, which is orders of magnitude larger than the electrical or optical switch time. Flip-chip bonding will reduce the shift of the wavelength, peak power, threshold current, and slope efficiency during VCSEL operation.

This article investigates steady-state nonequilibrium conditions in metal–oxide–semiconductor (MOS) capacitors. Steady-state nonequilibrium conditions are of significant interest due to the advent of wide-gap semiconductors in the arena of MOS (or metal–insulator–semiconductor) devices and due to the scaling of oxide thickness in Si technology. Two major classes of steady-state nonequilibrium conditions were studied both experimentally and theoretically: (i) steady-state deep depletion and (ii) steady-state low level optical generation. It is found that the identification and subsequent understanding of steady-state nonequilibrium conditions is of significant importance for correct interpretation of electrical measurements such as capacitance–voltage and conductance–voltage measurements. Basic implications of steady-state nonequilibrium conditions were derived for both MOS capacitors with low interfaces state density Dit and for oxide semiconductor interfaces with a pinned Fermi level. Further, a photoluminescence power spectroscopy technique is investigated as a complementary tool for direct-gap semiconductors to study Dit and to monitor the interface quality during device fabrication.

The activation efficiencies of implanted Si, Be, and C in GaAs0.93P0.07 have been measured in the annealing range 650–950 °C. Be provides much higher sheet hole densities than C, even when the latter is coimplanted with Ar to enhance the electrical activity. The maximum activation efficiency of Be is ∼60% at a dose of 5×1014 cm2 whereas that of C is an order of magnitude lower. Si produces donor activation percentages up to ∼20% under optimized annealing conditions. Capless proximity annealing is adequate for surface preservation up to ∼950 °C, as measured by scanning electron microscopy and atomic force microscopy. Photoluminescence measurements provide evidence that nonradiative, damage‐related point defects remain in the GaAsP even after annealing of 950 °C.

Properties of Ga2O3 thin films deposited by electron‐beam evaporation from a high‐purity single‐crystal Gd3Ga5O12 source are reported. As‐deposited Ga2O3 films are amorphous, stoichiometric, and homogeneous. Excellent uniformity in thickness and refractive index was obtained over a 2 in. wafer. The films maintain their integrity during annealing up to 800 and 1200 °C on GaAs and Si substrates, respectively. Optical properties including refractive index (n=1.84–1.88 at 980 nm wavelength) and band gap (4.4 eV) are close or identical, respectively, to Ga2O3 bulk properties. Reflectivities as low as 10−5 for Ga2O3/GaAs structures and a small absorption coefficient (≊100 cm−1 at 980 nm) were measured. Dielectric properties include a static dielectric constant between 9.9 and 10.2, which is identical to bulk Ga2O3, and electric breakdown fields up to 3.6 MV/cm. The Ga2O3/GaAs interface demonstrated a significantly higher photoluminescence intensity and thus a lower surface recombination velocity as compared to ...

Carbon-doped GaAs epitaxial layers were grown by low-pressure (30 Torr) organometallic vapor phase epitaxy using tris-dimethylaminoarsenic (DMAA) as the As precursor and carbon tetrachloride as the doping source. The epilayers were characterized by Hall measurements, secondary ion mass spectrometry, and infrared absorption. Hole concentrations exceeding 1020 cm-3 were obtained at a growth temperature of 550°C while still maintaining a featureless surface morphology. Typically 25–50% of the carbon acceptors were passivated by hydrogen despite the absence of an As-H bond in the DMAA precursor molecule. Rapid thermal annealing of the GaAs: C epilayers at 550°C for 90 s effectively removes the hydrogen and increases the hole concentration. Subsequent annealing of these layers under an ambient of DMAA in helium at 550°C for 120 s reintroduced the hydrogen at comparable concentrations to the as-grown layers, suggesting that the DMAA is probably the major source of hydrogen.

We have investigated the temperature characteristics of 850 nm, intra-cavity contacted, shallow implant-apertured, vertical-cavity surface-emitting lasers. The devices were fabricated with 7 μm diameter apertures and exhibited multimode behavior. Device lasing is observed up to 80 °C. The slope efficiency of the devices decrease from 0.29 to 0.20 W/A over the temperature range of 20–80 °C. From threshold temperature dependence data, the characteristic temperature is 78 °C. The fundamental optical mode of the devices shifts to longer wavelengths 0.11 nm/°C. The thermal resistance of the devices, determined experimentally, is 1.95 °C/mW.

We study the nonlinear properties of bulk AlGaAs and GaAs/AlGaAs multiple quantum wells(MQW) below the half‐band‐gap energy using subpicosecond pulses between 1.65 and 1.7 μm. In the bulk material we find a value for the nonlinear index n 2 = +3.6× 10−14 cm2/W and a two‐photon absorption coefficient β = 0.26 × 10−4 cm/MW. In the MQW we measure an n 2 up to 2.4 times larger, and we attribute this enhancement to a stronger 1S‐exciton intermediate state. The β value is up to 25 times larger in the MQW. This larger value may result from midgap states that resonantly enhance the virtual intermediate state in two‐photon absorption and act as a real transition in a two‐step absorption process. The resulting figure of merit (2n 2/βλ) for the bulk (MQW)material is 17 (1.6), which means that these semiconductors below half band gap are appropriate for all‐optical switching and quantum optics applications. We confirm that n 2 is instantaneous on the 300 fs time scale of our pulses from self‐phase‐modulation spectra as well as time‐resolved pump‐probe measurements. However, we find an intriguing exchange of energy between the two orthogonal axes as evidenced by the signal along the probe axis following the negative derivative of the pump intensity. This result may be explained by self‐phase modulation of the pump combined with a low‐frequency Raman process that couples the modes along orthogonal axes.

We present a detailed theoretical study on the optical and L–I characteristics of implant-apertured index-guided vertical-cavity surface-emitting lasers. Our theory is based on a beam propagation method combined with thermal, gain, and rate-equation models. Spatial hole burning and modal competition are taken into account. Our results are in excellent agreement with the experimental data and show the effect of the current aperture size (determined by the ion implant) on the modal performance of these devices. In particular, the current-aperture size can be fixed independently from the index-guide size to obtain minimum threshold, single-mode operation.

We show that two-photon photocurrent imaging can be used to nondestructively study vertical cavity surface emitting lasers on a microscopic level. In particular, we study the aperture isolation created by shallow ion implantation. The combination of two-photon backside imaging and a probe station is ideal for internal and full wafer characterization. The required peak and average power levels for testing can be easily satisfied by available compact ultrafast laser sources, making the technique practical and user friendly.

Electron cyclotron resonance (ECR) microwave plasma etching of In0.2Ga0.8As-GaAs strained multi-quantum well structures in PCl3Ar discharges is reported. The use of low DC self-biases ( or=150 V) erosion of the metal mask and trenching at the base of the sidewall are evident.

Using metal organic chemical vapor deposition, we have fabricated self-organized quantum dots that emit efficiently at 1.3 μm at room temperature. They are grown on GaAs and consist of InAs covered with an InGaAs cap layer. Their density is 2×1010 cm−2 as determined by transmission electron microscopy. Room-temperature photoluminescence shows a 36 meV broad line at 1.3 μm, corresponding to the quantum-dot ground state, with excellent uniformity across the wafer. The efficiency of this emission is reduced only by a factor of 4 with respect to low temperature showing the high quality of the sample.

We have demonstrated the first Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) insulated gate n-channel enhancement-mode In/sub 0.53/Ga/sub 0.47/As MOSFET's on InP semi-insulating substrate. Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) was electron beam deposited from a high purity single crystal Ga/sub 5/Gd/sub 3/O/sub 12/ source. The source and drain regions of the device were selectively implanted with Si to produce low resistance ohmic contacts. A 0.75-/spl mu/m gate length device exhibits an extrinsic transconductance of 190 mS/mm, which is an order of magnitude improvement over previously reported enhancement-mode InGaAs MISFETs. The current gain cutoff frequency, f/sub t/, and the maximum frequency of oscillation, f/sub max/, of 7 and 10 GHz were obtained, respectively, for a 0.75/spl times/100 /spl mu/m/sup 2/ gate dimension device at a gate voltage of 3 V and drain voltage of 2 V.

We have fabricated high power carbon‐doped InGaAs/AlGaAs lasers using an impurity‐induced layer disordering process to define the active region. The advantage of carbon doping is that it exhibits significantly lower diffusivity compared to other p‐type dopants, thereby avoiding displacement of the p‐n junction, even at the high temperatures and long diffusion times required by the disordering process. Secondary ion mass spectrometry (SIMS) measurements before and after Si diffusion show the p‐n junction position to be unchanged during processing. The carbon was introduced using CCl4 as an extrinsic precursor, giving improved control over doping levels and ternary growth conditions that is not available with intrinsic carbon doping. Thresholds of 20 mA and slope efficiencies of 0.44 mW/mA at 25 °C were obtained for lasers with cavity lengths of 500 μm and coated facets.

We report on the first demonstration of an enhancement-mode p-channel GaAs metal oxide field effect transistor (MOSFET) realized directly on GaAs semi-insulating substrate with a fully ion-implant technology. The device, with a 40/spl times/50 /spl mu/m/sup 2/ gate geometry, shows very good DC characteristics with transconductance of 0.3 mS/mm and an excellent gate breakdown field greater then 3 MV/cm.

We report a III-V based metal oxide semiconductor field effect transistor (MOSFET) technology using Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) as the gate insulator. Enhancement-mode p- and n-channel, depletion-mode n-channel GaAs MOSFETs, and enhancement-mode n-channel In/sub 0.53/Ga/sub 0.47/As MOSFETs were demonstrated.

We have investigated InGaAs MOSFETs using a mixture of Ga/sub 2/O/sub 3/ and Gd/sub 2/O/sub 3/ as the gate dielectric evaporated from a high-purity single-crystal Gd/sub 3/Ga/sub 5/O/sub 12/ source. We report the first Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) insulated gate n-channel enhancement-mode In/sub 0.53/Ga/sub 0.47/As MOSFETs on an InP semi-insulating substrate. A 0.75/spl times/50 /spl mu/m/sup 2/ gate device exhibits an extrinsic transconductance of 190 mS/mm which is an order of magnitude improvement over previously reported values. The current gain cut-off frequency and the maximum frequency of oscillation are 6.8 and 7.8 GHz, respectively.

The carbon doping properties of GaAs grown by low pressure (30 Torr) organometallic vapor phase epitaxy at 520–700 °C with CCl4 as the dopant precursor were compared for the four possible combinations of trimethylgallium (TMGa), triethylgallium (TEGa), arsine (AsH3), and tertiarybutylarsine (TBAs). Secondary ion mass spectrometry (SIMS), Hall measurements, and infrared absorption were used to characterize the GaAs:C layers. Very high C‐doping concentrations (∼1020 cm−3) could be obtained using either TMGa or TEGa and AsH3. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor over the growth temperature range examined. Hydrogen at significant concentrations (1–6×1019 cm−3) was detected by SIMS in GaAs: C layers grown at ≤550 °C utilizing all four combinations of Ga/As precursors. The existence of electrically inactive C‐H complexes was confirmed by observation of the C‐H stretching mode at 2635 cm−1. A post‐growth...

High quality AlxGa1−xAs has been grown by low‐pressure (30 Torr) organometallic vapor phase epitaxy (OMVPE) using a novel precursor, trimethylamine alane (TMAAl), as the aluminum source. The epilayers exhibited featureless surface morphology, very strong room‐temperature photoluminescence (PL), and excellent compositional uniformity (x=0.235±0.002 over a 40 mm diameter). The residual carbon incorporation, which determined the background doping, depended largely upon the choice of gallium precursor. Using triethylgallium, carbon incorporation could be largely suppressed ([C]≪1016 cm−3). The carbon‐related emission intensity was less than the bound exciton emission in low‐temperature (1.6 K) PL even at excitation powers as low as 50 μW cm−2. By sharp contrast, the use of trimethylgallium led to much higher C concentrations (2–5×1017cm−3). Under appropriate conditions, therefore, the use of TMAAl produces extremely high purity AlGaAs of superior quality to AlGaAs grown using conventional precursors.

The addition of SF6 to CH4/H2 discharges is shown to produce a significant increase in the selectivity for dry etching of both InGaAs and InP over AlInAs. The selectivity is a strong function of the dc bias on the sample during the reactive ion etching, with equirate removal of InGaAs and AlInAs for biases above 300 V. For lower bias values, the etch stop mechanism is related to the formation of Al‐F and In‐F species on the AlInAs surface, as evidenced by x‐ray photoelectron spectroscopy. The use of SF6 allows independent variation of the ratio of F to the other reactive species, in comparison to the use of fixed ratio gases such as C2H4F2 or CH3F.

This paper is a review of the incorporation and behaviour of carbon in group III–V materials. Both vapour phase epitaxy and growth in ultra high-vacuum environments are covered. Particular attention is given to the factors which influence the carbon-uptake rate such as the growth temperature, ratio of group V to group III materials and parasitic interaction with other species at the growth front. Among the latter, the role of hydrogen is crucial not only to the understanding of the incorporation of carbon but also to its behaviour in the lattice. Consequently, this issue is thoroughly discussed for both growth methods. Potential sources for the introduction of carbon to the growth front are also compared in the light of their utility for obtaining high well-confined acceptor profiles, such as are required in the latest-generation electronic and photonic devices. Finally, the material quality and dopant stability which can be obtained with carbon-doped materials will be briefly reviewed and, where possible, contrasted with that which can be obtained with other p-type dopants.

We present measurements of the nonlinear index n2 and two-photon absorption coefficient β as well as time resolved pump-probe data for both bulk AlGaAs and GaAs/AlGaAs multiple quantum well waveguides near half-gap at 1.68 μm. The figure of merit (2n2/βλ) [1] for the bulk (MQW) material is 17 (1.6), which means that these semiconductors below half bandgap are appropriate for all-optical switching and quantum optics applications. The β value is up to 25 times larger in the MQW. This larger value may result from mid-gap states that act as a stepping stone in two-photon absorption (TPA). The mid-gap absorption should not be fundamental to MQW material provided that caution is exercised during the growth to avoid impurities and interface states. We confirm that n2 is instantaneous on the 300 fs time scale of our pulses from self-phase-modulation spectra as well as time-resolved pump-probe measurements. However, we find an intriguing exchange of energy between the two orthogonal axes with the signal along the probe axis following the negative derivative of the pump. This result may be explained by self-phase-modulation of the pump combined with a low frequency Raman gain between orthogonal axes.

We overview and summarize the progress of the spectral phase encoded time spreading (SPECTS) optical code division multiple access (O-CDMA) technology. Recent progress included a demonstration of a ...

p-n junctions have been formed in lightly n-type (1017cm−3) bulk, single-crystal ZnO substrates by diffusion of P from a Cd3P2, arsenic and red phosphorous dopant source in a closed-ampoule system. The P incorporation depth was found to be ∼200nm after diffusion at 550°C for 30min, as determined by secondary ion mass spectrometry profiling. The resulting structures show rectification, with on-off current ratios of ∼70 at +3∕−5V. The forward current ideality factor was ⩾2, consistent with multiple current transport mechanisms present in the junction, such as defect-assisted tunneling and conventional carrier recombination in the space-charge region via midgap deep levels. The forward turn-on voltage, VF was ∼4V at 300K with a specific on-state resistance (RON) of ∼21mΩcm2. The activation energy of the forward current at low forward biases was ∼1.4eV. This is also consistent with carrier recombination in the space charge region via a midgap deep level.

Inductively coupled plasma etching of InGaP, AlInP and AlGaP in BI3 or BBr3 discharges was investigated as a function of source power, dc chuck bias and plasma composition. InGaP etches at the fastest rates (>6000 A min−1) in both chemistries, followed by AlGaP. It is found that AlInP provides an excellent etch stop for the other two materials in both mixtures. The InGaP surface morphology improves with increasing BI3 or BBr3 content, and with increasing dc chuck bias. The etched features for this material are highly anisotropic. Etch selectivities for InGaP over SiO2 and SiNx of ⩾8 are obtained in both plasma chemistries, and there is no etch incubation time with either mixture, indicating that both can scavenge the native oxide on InGaP, AlGaP and AlInP.

We have successfully fabricated depletion mode GaAs metal–oxide–semiconductor field effect transistors using Ga2O3(Gd2O3) as the gate oxide and an oxygen implant isolation technique. Growth of the device structure including the deposition of Ga2O3(Gd2O3) was performed in a multichamber molecular beam epitaxy system. A 1 μm×100 μm device shows excellent dc and microwave characteristics with low output conductance. Complete pinchoff at Vg=−2.5 V and operation in the accumulation mode of up to Vg=2.5 V were measured. The maximum transconductance was 100 mS/mm, with a high drain current density of 315 mA/mm. Microwave testing yielded a fT of 14 GHz and a fmax of 35 GHz.

Etch rates for InP, InAlP, and InGaP can be controlled between ∼1500 A/min and ≳1 μm/min by varying the microwave power, rf power, or N2 composition in BCl3N2 discharges under electron cyclotron resonance conditions. The surface morphology of InGaP is poor at low microwave power (250 W), but becomes very smooth at high powers (1000 W). InP has exactly the opposite dependence on microwave power, while InAlP shows little change in morphology over a wide range of powers. The high ion current under electron cyclotron resonance conditions enables etching of In‐based semiconductors without the need for high sample temperatures to enhance desorption of InClX species.

Etch rates up to 7000 A/min for InP and 3500 A/min for GaAs are obtained for high microwave power (1000 W) CH4/H2/Ar electron cyclotron resonance plasma etching. Preferential loss of the group V element leads to nonstoichiometric, unacceptably rough surfaces on In‐based binary semiconductors at microwave powers ≥400 W, regardless of plasma composition. Both Ga‐ and Al‐based materials retain smooth, stoichiometric surfaces even at 1000 W, but the rates are still much slower than for Cl2 plasma chemistries. The results suggest that CH4/H2 plasmas are not well suited to electron cyclotron resonance systems operating at high powers.

The dry etching characteristics of InP and GaAs using CH4/H2 plasmas produced by two different electron cyclotron resonance (ECR) source configurations were examined in terms of surface morphology, stoichiometry, etch rate and anisotropy and finally the etch uniformity on 3‘φ wafers. Both the multipolar resonant cavity ECR source and the more conventional high‐profile magnetic mirror configuration produce high ion densities (∼7×1011 cm−3 at 1000 W) in 1 mTorr CH4/H2/Ar discharges, although the mirror source has slightly faster etch rates for both InP and GaAs. The etching becomes more anisotropic as the rf power to the chuck position is increased, and the rates fall for substrate temperatures below −10 °C, although the stoichiometry of the near‐surface region of InP is slightly better under these conditions. The optimized etch uniformity is ≤±2% for both sources and in general is better for high rf and microwave powers. Manual tuning of the multipolar source is simpler than for the mirror source and it is a little more stable during operation, with fewer of the mode jumps observed for the mirror configuration.

Fabrication of submicron high electron mobility transistors (HEMTs) involves dry etch removal of GaAs from an underlying AlGaAs or InGaAs stop layer. The etch selectivity is achieved by formation of AlF3 on AlGaAs, or InCl3 and InF3 on InGaAs, which must be removed before processing can proceed. Wet chemical cleaning has difficulty in such a situation because of surface tension effects. We have investigated use of electron cyclotron resonance (ECR) H2 or Ar discharges, or hexafluoroacetylacetone (HFAC) vapor, for in situ dry etch cleaning of HEMTs exposed to low‐bias BCl3/SF6 discharges. The HFAC vapor can remove most of the remnant fluorine, but is effective only when the sample is heated above ∼250 °C. This relatively high temperature is not compatible with in situ cleaning of the etched device. Low‐bias (−75 V) sputter cleaning with an Ar discharge removes all remnant Cl and ∼40% of the F, but direct‐current biases above −125 V are required for complete cleaning, and this ion bombardment can lead to da...

Epitaxial growth of InP and GaAs (AlGaAs) in narrow (∼1 μm wide) trenches and around mesas formed by highly anisotropic dry etching was performed by low‐pressure (30 Torr) organometallic vapor phase epitaxy (OMVPE) and metalorganic molecular beam epitaxy (MOMBE). For the [110] oriented trenches and mesas, MOMBE produced highly selective regrowth of both materials under normal growth conditions. By contrast, it was necessary to add CCl4 to the growth chemistry in OMVPE to eliminate deposition on the SiNx mask during growth in trenches and around mesas. Due to growth rate enhancement near the edge of the masked regions, acceptable control of the growth thickness in OMVPE could only be obtained for the case of mesas, but not for narrow trenches.

The characteristics of plasma etching of InP, InAs, InSb, GaAs, AlGaAs, GaSb, AlInAs, InGaAs, and AlInP in microwave (2.45 GHz) discharges of methyl‐, ethyl‐, and propyl‐iodide have been examined with respect to etch rates, surface morphology, damage introduction, and etch anisotropy. The etch rates for all of these semiconductors are somewhat faster than for conventional CH4‐based discharges under the same conditions of direct‐current bias, pressure, and microwave power, but are not as fast as with HI discharges. Polymer deposition on the mask and within the chamber occurs as with CH4‐based mixtures, but is minimized at low pressure (≤10 mTorr) and with H2 dilution. The etched surface morphologies are smooth over a wide range of plasma parameters and show roughness only under conditions of significant polymer deposition. Chemical analysis by Auger electron spectroscopy and x‐ray photoelectron spectroscopy also shows that the near surface of the etched samples retains its stoichiometry under most conditio...

A selective wet chemical etching solution for removal of Al0.5In0.5P from GaAs based on HCl:H2O has been developed. Controllable etch rates from 600 A min−1 at 1HCl:30H2O to 6000 A min−1 at 1HCl:5H2O at 25 °C are obtained. The etch rate is thermally activated of the form R∝exp(−Ea/kT) where Ea=12.4 kCal mol−1, consistent with reaction‐limited etching. Dry etch rates of AlInP in PCl3/Ar, CCl2F2/Ar, or CH4/H2/Ar electron cyclotron resonance discharges are all

We demonstrate a hybrid time-domain chirp switch (TDCS) in which the nonlinear chirper is an AlGaAs waveguide and the soliton dispersive delay line is a polarization-maintaining fiber. The hybrid TDCS can restore timing in a switching or transmission system, and when combined with an optical amplifier, it can act as an ultrafast, all-optical regenerator for soliton pulses. The timing restoration concept is applicable to other non-linear materials with negligible walk-off, and the acceptable time window can be tailored by adjusting the width and intensity of a reference pulse.

The etch rate, surface morphology and atomic composition, and depth of hydrogen passivation of Si dopants in n‐type GaAs and AlGaAs have been examined as a function of the temperature of the sample during reactive ion etching in C2H6/H2. While there is no temperature dependence of the etch rate of AlGaAs over the range 50–350 °C, the etching of GaAs shows an increase of a factor of 2 between 150 and 250 °C, decreasing at higher temperatures. The As‐to‐Ga ratio in the near‐surface region of GaAs remains unchanged over the whole temperature range investigated and there is no polymer deposition. The etched surface morphology is smooth for both GaAs and AlGaAs for all temperatures while the depth of Si dopant passivation by hydrogen shows an increase with increasing substrate temperature during the etching treatment.

Summary form only given. The VCSELs of this work are based on an implanted-aperture, index-guided, lateral current injected, top dielectric mirror GaAs quantum well 850 nm design. The thermal simulation employs quasi-three dimensional finite difference analysis to calculate the temperature, thermal resistance and the rise time of temperature at a fixed bias to calculate the nonuniform heat source distribution.

The growth of GaAs layers on silicon substrates is under extensive investigation with a view to achieving the integration of GaAs-based optoelectronic devices with Si integrated circuit technology. The large lattice mismatch between Si and GaAs (-4%) together with the differences in the thermal expansion coefficients between the two materials results in a highly stressed interface. Several different approaches have been undertaken in attempts to reduce the dislocation density of the GaAs layer. The inclusion of graded composition GaAsP ‘buffer’ layers, intermediate Ge layers and the inclusion of strained layer superlattices in the growth regime have been reported by many workers. Growth of GaAs directly on Si has been reported to yield GaAs heteroepitaxial films suitable for electronic applications such as FETs and low threshold AlGaAs/GaAs double heterostructure injection lasers.