Molecular Beam Epitaxy Material Research Articles

CW IMPATTs made from silicon molecular beam epitaxy material

CW-IMPATT diodes for W-band operation are fabricated from Silicon Molecular Beam Epitaxy material. Using different preparation techniques, the active layer of single drift structures is grown at 750 °C and 550 °C. Doping is performed by molecular beams from Sb (n-type) or Ga (p-type) effusion cells. The influence of the p+-doping level on the series resistance of the diode is investigated. Measurements of efficiency as a function of the active region data deliver fine design rules. The output power is 450 mW at 87 GHz from diodes mounted in a hermetically sealed package on a diamond heat sink.

Molecular beam epitaxy growth of high performance GaAs power field effect transistors

GaAs power field effect transistors (FET’s) with the highest power output per unit gate width (0.46 W/mm) reported to data at Ka‐band frequency were fabricated using molecular beam epitaxy material with active layer doping of 3.6×1017 cm3. Power output of 110 mW and conversion efficiency of 11% were achieved with half‐micron gate GaAs FET’s in a 30 GHz amplifier with an associated gain of 3.4 dB. This report describes the molecular beam epitaxy (MBE) growth conditions and results of characterization of the power FET.

Interband transitions in molecular-beam-epitaxial AlxGa1−xAs/GaAs

Interband transition energies for AlxGa1−xAs layers grown by molecular-beam epitaxy (MBE) techniques have been determined using the electrolyte electroreflectance (EER) technique. The observed data fit quadratic relations for E0, E0+Δ0, E1 and E1+Δ1 to describe variations of energy with composition. Although the x values were not accurately known, the internal consistency of the data is excellent. Given a single bowing parameter we show that accurate values of x can be determined. The EER technique can provide x values with an accuracy better than 0.02 and information on changes in x as small as 0.002. It is thus ideally suited for studying MBE materials.

Photoluminescence studies of silicon molecular beam epitaxy layers

Photoluminescence spectra are used to investigate inadvertent impurities in Si molecular beam epitaxy (MBE) layers. The spectra show free exciton and condensed exciton (electron-hole drop) features which are indicative of good crystalline quality. Electrically active shallow impurities are identified from near-gap bound exciton features. In one layer radiative recombination at dislocations is dominant. For the first time using an optical technique carbon is shown to be a persistent impurity in Si MBE material. This technique provides a test for inadvertent carbon incorporation at levels which may otherwise be difficult to detect in thin epitaxial layers.

A UHV-compatible round wafer heater for silicon molecular beam epitaxy

An ultrahigh vacuum-compatible round wafer heater for silicon molecular beam epitaxy (MBE) is described. The assembly incorporates a hot tantalum filament and is capable of heating a single 2 in. diameter silicon wafer to a temperature of 1200 °C at a rate of 350 °C/min with a total power dissipation of 600 W. Best results are obtained when a silicon diffuser is positioned between the wafer and the filament. In this case, the observed temperature variation across the wafer is ≤16 °C, and virtually slip-free epitaxial layers can be grown. The quality of epitaxial layers grown using this heater is, in general, the highest we have yet observed for silicon MBE material, with line dislocation density below 103/cm2.

Molecular Beam Epitaxy of III-V Compounds: Application of MBE-Grown Films

The performance of devices fabricated from materials grown by molecular beam epitaxy (MBE) can ideally be used to judge this new film growth technique. From the beginning, microwave and optoelectronic devices have been fabricated from MBE-grown GaAs and AlxGa1_xAs. Initially this work was done mainly at Bell Telephone Laboratories. Fabrication and performance of various devices obtained from MBE material were summarized in excellent reviews by Cho & Arthur (1) and by Cho (2). In the first decade, emphasis was on the MBE production of standard device structures exhibiting characteristics comparable with or even superior to those fabricated by the more conventional growth and processing techniques. Excellent results were obtained for MBE-grown GaAs devices including varactor diodes (3-5), mixer diodes (5, 6-9), IMPATT diodes (10), Gunn diodes (11), MESFETs (12-17), optical waveguides (18-23), and DH injection lasers (24-46). The unique features of MBE have been further applied to more complex device structures involving novel processing steps such as lateral dimensional control as well as metal-semiconductor and oxide-semiconductor heterojunction formation in a single growth cycle. The limits of the MBE technique for the production of novel device structures have not yet been reached.