Uniform Radial Flow Epitaxy of Indium Phosphide and Indium Gallium Arsenide Using Halide Transport
Abstract
A novel epitaxial technique called uniform radial flow epitaxy (URFE) is described for growing thin (< 20A) layer heterostructures of III-V compound semiconductors. The geometry of the URFE reactor is similar to the configuration used in vapor levitation expitaxy (VLE) but the growth vapors are delivered to the top of the substrate which is placed on a paddle. This design avoids the difficulties in fabricating the quartz reactor used in VLE and can use samples of arbitrary shape. The performance of this epitaxial system was demonstrated by growing InGaAs/InP heterostructures using the halide growth process. An experimentally useful approach to defining the reactant gas composition is presented and was used to investigate the growth of InP epitaxial layers over a range of reactor conditions. The surface morphology and etch rate of InP substrates are reported for HCl concentration and H_2 flow rate during the in situ etching used to prepare the substrate for epitaxial growth. Specular surfaces are obtained for many etch conditions provided the etch depth is limited to 1 mu m. The growth rate of InP epitaxial firms grown in this study was controlled by the concentration of indium in the gas phase. Indium was found to incorporate into the growing film at a slower rate than phosphorus. Raman Spectroscopy, Photoluminescence, and Hall effect were used to characterize the crystal structure, optical emission, and transport properties of InP films. The growth of In_{rm x}Ga_{rm 1-x} As alloys under different reactant gas compositions was investigated. The growth rate was found to depend only on the total concentration of group III elements and the film composition to depend only on the ratio of indium to gallium in the gas phase. Hence, the alloy composition of the solid film and its growth rate can be independently controlled using the growth process reported in this work. Parasitic wall deposition is shown to seriously reduce the growth rate of the film and is believed to limit the control of the alloy composition. Excellent layer uniformity was obtained using the URFE reactor. Layer thickness was found to vary no more than 5 to 8 percent for a 1000 A InGaAs layer over a one inch square sample. Transmission Electron Spectroscopy was used to resolve InGaAs layers less than 20 A thick in a multilayer InGaAs/InP heterostructure. Raman Spectroscopy was used to measure the layer strain in pseudomorphic InGaAs films (<100 A) prepared using this reactor.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1992
- Bibcode:
- 1992PhDT........74A
- Keywords:
-
- INDIUM PHOSPHIDE;
- INDIUM GALLIUM ARSENIDE;
- Physics: Condensed Matter