Ram R. Saxena

The organometallic vpe growth of GaSb and GaAsl−xSbx using trimethylantimony

The organometallic vapor phase epitaxial (OMVPE) growth of GaSb and GaAsl−xSbx (0 ≤ × ≤ 0.26, 0 .64 ≤ × ≤1) is discussed. Trimethylgallium and trimethylantimony are used as the Ga and Sb source, respectively. Most GaAs1× Sbx growths are done using arsine, but the use of an alternate arsenic source, trimethylarsenic, is also discussed. In contrast to most arsenic-containing alloys, both GaSb and Sb-rich GaAs1−x Sbx are grown under Group III-rich conditions. The total input flux as well as the ratio of the input chemicals must be closely regulated. In particular, growth of GaAsl−xSbx requires careful control of the trimethylantimony-to-total Group V ratio, since arsenic preferentially incorporates into the crystal.

The growth and characterization of uniform Ga1-xInxAs (X ≤.25) by Organometallic VPE

Compositionally uniform Ga1-xInxAs epitaxial layers with 0 ≤ x ≤ 0.2 5 have been grown by organometallic VPE on ◃100▹ GaAs substrates. Compositional uniformities of ±0.25 InAs percentage and ±5% thickness over a 3-cm long wafer have been achieved and are essentially independent of small changes in reactor geometry such as the angle of the susceptor tilt or wafer position on the susceptor. Growth has also been demonstrated at x = 0.52. The Ga1-xInxAs is grown using trimethylgallium (TMGa), triethylindium (TEIn) or trimethylindium (TMIn), and trimethylarsenic (TMAs). The use of TMAs eliminates the roomtemperature gas-phase reaction between AsH3 and either TEIn or TMIn, and allows one atmospnere pressure growth conditions to be used without any special mixing arrangements in the reactor. The comparative effects of using TEIn or TMIn as the In source are discussed in terms of crystal quality. Data on crystal composition as a function of gas phase composition and growth rate as a function of composition are presented, and n doping and carrier mobilities and p doping of Ga.80In.20As ars characterized. The vapor pressure of TMIn at 0°C is determined to be 0.21 mmHg.

Studies of GaAs and AlGaAs layers grown by OM-VPE

Abstract The epitaxial growth of GaAs by OM-VPE is discussed as effected by the orientation of the substrate, the input fluxes, and the growth temperature. The growth rate is studied under varying conditions and the uniformity along the susceptor is investigated. It is shown that the observations point to a diffusion-controlled mass transport-limited growth mechanism. Recent results of improvement in the quality of AlGaAs layers grown by OM-VPE for solar cell applications are also described.

Solar cell development at Varian

Varian Associates is engaged in development and pilot production of a wide variety of compound semiconductor photovoltaic devices. The various facets of this work are described. Included is pilot production of AlGaAs/GaAs solar cells, various spectrum splitting devices and approaches, and a monolithic integrated GaAs solar cell array.