A technology based on a combination of selective implantation for lateral patterning and a following large area regrowth by molecular beam epitaxy (MBE) is introduced. The technology allows the monolithic integration of devices with different vertical layer sequences on s.i. GaAs substrates in a quasi planar way, e.g. a heterojunction field-effect-transistor (HFET) with a Schottky diode or a MESFET with a Schottky diode. Selective high resistive (>109 Ω/sq) and highly conducting (<20Ω/sq) buried layers are fabricated by high temperature stable oxygen and silicon implantation, respectively. The following MBE regrowth of epitaxial layers yields to an excellent surface morphology. HFET structures with pseudomorphic AlGaAs/InGaAs/GaAs heterostructures grown on implanted substrates exhibit a strong photoluminescence response. Carrier densities up to 2.0×1012cm−2 (1.6×1012cm−2) and Hall mobilities of 6150 cm2/Vs (17700 cm2/Vs) at 300 K (80 K) in the dark are achieved. The material quality is drastically improved by substrate preparation and in-situ cleaning prior to MBE regrowth.

Strained layer In0.2Ga0.8As/GaAs quantum-well (QW) lasers have been used to pump Erbium Doped Fiber Amplifiers for use in opto-electronic communication systems. These InGaAs/GaAs Q-W lasers grown as graded index separate confinement heterostructures (GRINSCH) emit at 980 nm and have exhibited low threshold current densities, high electrical to optical power conversion efficiencies, low noise, and low temperature sensitivities [1–3]. Recently there has been much attention toward the growth and fabrication of devices containing short period superlattices of (InAs)m/(GaAs)m or (GaAs)m/(AlAs)n compositions [4–9]. Indeed the growth of inverted MODFET structures using a (GaAs)/(AlAs) superlattice barrier in place of an AlGaAs random alloy exhibited an increase in low temperature mobility due to reductions in the number of impurities and interface roughness [7]]. Can the optical properties of strained layer InGaAs/GaAs Q-W lasers also be improved by growing an (InAs)/(GaAs)4 short period superlattice as the active layer in place of the In0.2Ga0.8 As random alloy?

This paper reports the fabrication of ridge waveguide lasers using a 6 period (InAs)1/(GaAs)4 superlattice active region in a GRINSCH laser structure. One period of the superlattice consists of 1 monolayer (ML) of InAs and 4 ML of GaAs. Thus the average In composition in the superlattice is 20%. This superlattice laser is an alternative to the In0.2Ga0.8As/GaAs random alloy quantum-well laser used as a pump source for Erbium Doped Fiber Amplifiers. In a single quantum well In0.2Ga0.8As/GaAs laser the active region is a thin layer (-70Å thick) sandwiched between GaAs barrier layers. The superlattice active laser reported here has 6 periods of (InAs)1/(GaAs)4 as the light emitting region of a total width comparable to a single quantum well of random alloy composition.

Strained-layer InGaAs/GalnAsP/GalnP separate-confinement-heterostructure quantum well lasers emitting at 980 nm have been developed. The lowest threshold current densities obtained for the single-quantum-well and three-quantum-well lasers are 72 and 150 A/cm2, respectively. The internal quantum efficiency is as high as 94 %, and the internal waveguide loss 5.4 cm−1. The transparency current density and gain coefficient are 33 A/cm2 per well and 0.091 μm A−1, respectively. High characteristic temperatures ranging from 220 to 280 K was obtained. The vertical and lateral full-width at half-maximum of the far-field pattern of the ridge waveguide laser are 47° and 13°, respectively. The results are comparable with the best values reported for the InGaAs/AlGaAs lasers.

Quasi-phase matching in AlxGa1−xAs heterostructure optical waveguides can be used for efficient second-harmonic (SH) generation. The efficiency of these devices depends on the linear and nonlinear optical properties of the component materials. We present measurements of the SH susceptibility variation in AlxGa1−xAs with Al concentration, for fundamental light at λ = 1.06 μ. The measured SH susceptibility decreases by an order of magnitude as the Al concentration is varied from x = 0 to x = 0.97. These measurements are used to evaluate the SH generation efficiency of AlxGa1−xAs heterostructures as the structural and material parameters are varied.

Simulations of reflectance spectra and electric field distributions for vertical-cavity structures were used in the computer aided design of epitaxial mirrors and lasers. The binary GaAs/AlAs superlattice alloys and AlxGa1−xAs random alloys that compose these structures were grown by molecular beam epitaxy. Photoluminescence, photoreflectance, reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and double crystal x-ray diffractometry were applied to characterize cavity and Bragg mirror layer thicknesses and alloy composition.

Optical channel waveguiding in AlGaAs multiple quantum well structures formed by compositional mixing implemented by focused ion beam (FIB) implantation is demonstrated. To achieve selective mixing, Si is FIB implanted with a dose of 5×1014 cm−2 followed by RTA at 950°C for 10 s. Raman microprobe spectra are used to characterize the lateral variation of mixing. Propagation loss in a channel waveguide is measured. Measurement of the waveguide mode field distribution allows for the determination of changes in refractive index due to mixing and an approximate mixing depth.

Results are presented on the fabrication of optical gratings on an Al0.3Ga0.7As/GaAs superlattice (SL) with equal 3.5 nm barrier and well widths, by using locally FIB-enhanced mixing. As the first step, the mechanism of the mixing was studied. Si++ was accelerated to 50 kV and lOOkV and implanted at doses ranging from 1013 to 1015/cm2. A rapid thermal anneal of 10 s at 950°C was utilized. The average Al inter-diffusion coefficient and length were calculated as a function of FIB dose from SIMS depth profiling. The mixing was significantly enhanced by the FIB implantation. The ion dose as low as l×1014/cm2 followed by RTA yields a mixing parameter of ∼90% and results in a two-order of magnitude increase in the diffusion coefficient, to a value of 4.5×10−14cm2/sec, in contrast to 1.3×10−16cm2/sec from RTA-only. The maximum mixing occurred in the region where neither Si ions nor vacancies have their maximum concentration. Instead, it coincides with the location of the positive maximum of the second derivative of the vacancy concentration profile. This fact suggests that in the time frame of RTA and with low dose, the diffusion of nonequilibrium point defects plays a major role in the process of enhancing Al-Ga interdiffusion. DBR optical gratings, consisting of thousands of spacing lines with 350nm period, were fabricated with a lOOkV FIB dose of 2×1013 andl×1014/cm2. Photoluminescence (PL) spectra were taken from the grating region as well as the unimplanted superlattice region. The PL intensity from cavity region of the DBR was about 16 times higher than that from the original SL. This PL enhancement was verified to occur in the cavity region only by spatially scanning over the entire sample. A possible mechanism for this PL enhancement is optical feedback provided by the gratings.

Epitaxial GaAs layers have been grown on saw-tooth-patterned (STP) Si substrates by metal-organic chemical vapor deposition and analyzed by transmission electron microscopy. The utilization of this special interface feature is effective in suppressing the formation of antiphase boundaries and reducing the threading dislocation density. The growth of GaAs has been studied with the epilayer thicknesses ranging from several hundred angstroms to several microns. Very flat growth front on (100) plane above the STP region is observed. The dislocation density decreases very rapidly in the area farther away from the interface. The dislocation configuration at this STP interface is very different from that at the extensively studied two-dimensional planar interface.

Chemical beam epitaxy (CBE) has been used to grow GaAs on silicon with a low defect density after etching in HF followed by a low temperature (600°C) in situ heat treatment. High resolution electron microscopy (HREM) and convergent beam electron diffraction (CBED) studies show the presence of 90° and 60° dislocations and some inversion domains.

In this work, we have compared, by using Transmission Electron Microscopy (TEM) techniques, the initial stages of epitaxial growth of GaAs on Si (100) by conventional MBE and ALMBE, trying to find the conditions necessary to achieve 2D growth at the earliest stage of deposition. Our results show that flat layers with a good surface coverage can be obtained by reducing the GaAs ALMBE deposition temperature down to 200°C.

We developed GaAs heteroepitaxy on a Si substrate by metalorganic vapor phase epitaxy (MOVPE) using tertiarybutylarsine (TBAs). In buffer layer growth at 450°C, the surface morphology and crystal quality of TBAs-grown films were slightly inferior to those of AsH3-grown films. At buffer layer growth below 400°C, the quality of TBAs-grown films improved. The GaAs films we grew using TBAs had a better quality than those grown using AsH2.

Thermal stress distributions in patterned GaAs/Si are studied by low temperature cathodoluminescence spectroscopy. The MOCVD-grown samples have ben patterned in the form of stripes either by selective etching or by selective GaAs/Si growth using a SiO2 mask. In this work, the relevant stress components are determined as functions of position for stripes with different width to thickness ratios from low temperature (10 K) GaAs cathodoluminescence spectra and the results are discussed in comparison with finite element elastic calculations.

Conventional GaAs-based laser diodes grown on Si substrates suffer from rapid degradation, which results from the deteriorations of optical and electrical characteristics. Electroluminescence observation shows that the optical deterioration is caused by the formation of dark-line defects. The current-voltage (I-V) characteristic of the p-n junction is degraded with aging, and results in an ohmic-like under a higher ambient temperature and a larger forward current. The deterioration of the I-V characteristic is caused by defect-accelerated impurity diffusion because the growth of GaAs on Si substrates (GaAs/Si) involves the high dislocation density, the large tensile stress and the large amount of Si near the GaAs/Si interface. A significant improvement in reliability has been achieved in the strain-relieved AlGaAs/InGaAs laser diode on Si grown with the InGaAs intermediate layer. The stress relief by the InGaAs active layer and the reduction of the dark-line defect formation by the InGaAs intermediate layer are required to fabricate reliable GaAs-based laser diodes on Si substrates.

We reported a waveguide-type optical switch fabricated on a Si substrate which utilized the Quantum Confined Stark Effect (QCSE). The prepared sample is an Al0.3Ga0.7As (cladding layer) / Al0.25Ga0.75As (guiding layer) double-heterostructure (DH) optical switch with a GaAs single quantum well (SQW) in the guiding layer by MOCVD. The absorption edge of the sample is measured by photocurrent method under reverse bias using a cw Ti: Sapphire laser for a light source. We measured about 10 nm shift of the absorption edge at -8 V from the sample with 8.3 nm SQW. This result demonstrates the Stark-shift effect of GaAs SQW on Si. A 2.5 μm-width ridge was formed by etching in the top cladding layer and the light traveling in the guiding layer was confined to a fundamental mode in vertical (parallel to growth direction) and horizontal direction. This switch showed 33.1 dB/mm modulation at 867 nm wavelength in -8 V bias.

A 1.35 μm wavelength GaInAsP / InP double heterostructure laser has been grown on Si substrate by low-pressure metalorganic chemical vapor deposition. The layers are grown directly on Si substrate coated with GaAs. Material characterization confirms the overall quality of the epitaxial layers, including excellent crystallinity and optical properties in addition to precision control over the growth, composition and doping of the different layers. Pulsed operation with output power of over 200 mW per facet was achieved at room temperature for a broad area laser with 20 μm width and 170μm cavity length.

We report the first InSb film growth on Si by low-pressure metalorganic chemical vapor deposition. High-quality layers of InSb have been grown on Si and GaAs substrates. InSb films displayed mirror-like morphology on both substrates. X-ray full width at half maximum of 171 arcsec on GaAs and 361 arcsec on Si for a InSb layer thickness of 3.1 μm were measured. Room-temperature Hall mobilities of 67,000 and 48,000 cm2/V.s with carrier concentration of 1.5×1016 and 2.3×1016 cm−3 have been achieved for InSb films grown on GaAs and Si substrates, respectively. A 4.8 μ-thick InSb film on GaAs exhibited mobility of 76,200 cm2/Vs at 240 K.

We report the first growth of InSb and GaAs epilayers upon a garnet (YIG = Y3Fe5O12) epilayer. The YIG was deposited using liquid phase epitaxy on a garnet (GGG = Gd3Ga5O12) substrate oriented in the [111] direction. The growth of the GaAs was carried out using laser ablation and no superlattice was used to buffer the lattice mismatch between YIG and GaAs. The growth of InSb was done by low-pressure metalorganic chemical vapor deposition. From x-ray diffraction analysis it was found that the GaAs and InSb were both (110) monocrystalline epitaxial layers.

The quality of SiGe/Si heterodevices recently could be improved by depositing on a SiGe buffer with a Ge grading. In house MBE grown structures reached 1.5 K mobilities of 173000 cm2/Vs. Also at room temperature (RT) the mobility is up to 4 times higher than in bulk Si or SiGe. HBTs in the discussed material system can exceed performances of conventional Si-homobipolar transistors, already with relaxed design rules. I briefly review on mesa - like SiGe HBTs with high fmax and fT around 50 GHz, owing to low base sheet resistances <1Kω□. In DC-operation high gains >400 or 13 000 at RT or 77K were obtained, n - and p - channel Si, SiGe and Ge MODFETs will be presented in more detail, n- MODFETs exhibit high transconductances above 300 mS/mm at RT and almost 1000 mS/mm at 77K. Different effects will be discussed, e.g. the influence of the gate to channel distance and effects of rapid thermal activation. Si/Ge heterosystems offer exclusive properties, e.g. the same mobility in a Si - 2DEG and a Ge - 2DHG. Complementary MODFETs (CMOD) can be envisaged. Furtheron the Si/Ge system allows the monolithic integration of heterodevices with high complexity Si - ICs (heterointegration).

SiGe alloys have been successfully applied to a number of semiconductor devices, including bipolar heterojunction transistors, field effect transistors (FET's), and optoelectronic devices and structures. This review paper will first summarize the results obtained to-date in bipolar transistors, highlighting the design flexibility and the trade-offs offered by SiGe heterojunction technology and bandgap engineering, like junction field/capacitance control, liquid nitrogen operation and complementary processes. The leverage of this technology in high speed circuits will be discussed, including the record 75 GHz fr and 60 GHz fmax heterojunction bipolar transistors, the achievement of sub-25 ps ECL ring oscillator delay, and the doubling of the mobility in p-MODFETs. The applications of this technology to optoelectronic devices, including detectors and waveguides, will also be reviewed, to extend the use of silicon technology to long wavelength communication technology and infrared imaging.

The effective transversal mobility of the minority carrier electrons in asymmetrically strained p-type Si1−x Gex -layers, grown on a Si (100) substrate, is studied as a function of boron doping concentration and Ge-content x. The experiments are based on the temperature dependence (290 to 400K) of the collector current enhancement of heterojunction bipolar transistors with a pseudomorphic Si1−x Gex-base. The interpretation of these results is based on new insights about the effective density of states in the valence band of these strained layers [1]. We will present first experimental evidence of the theoretical calculations in [1]. From this we will derive then the value of the NcNv -product for the strained Si1−x Gex-alloy. This allows to extract the ratio of the electron mobility in Si and strained Si1−xGex. We found an enhancement of the mobility when the B-doping level is around 1018 cm−3 and 0.08<x<0.16. At higher values of the Ge-content and the doping level, the enhancement is reduced again.