Photoluminescence and electrical properties of close space vapor transport GaAs epitaxial layers

Close spaced vapor transport (CSVT) epitaxial layers have been grown under water vapor partial pressure p ranging from 5×10−2 to 5 mm Hg for source temperatures of 800 and 850 °C and a substrate temperature of 730 °C, using undoped high-purity GaAs as source material and 〈100〉 chromium doped high-resistivity GaAs as substrate. From Hall measurements, all layers were found to be n-type with a majority carrier concentration in the range of (2–3) ×1017 cm−3 and a mobility 3100–3600 cm2 V−1 s−1 as p varies from 5.0 to 5×10−2 mm Hg. Photoluminescence measurements show the following dominant recombination processes: an exitonic peak at 1.514 eV, a free band acceptor at 1.498 eV, a donor acceptor at 1.490 eV, and two peaks involving complexes at 1.47 and 1.42 eV. These peaks depend on the water vapor pressure: for low values of p only the exitonic peaks exist; as p increases the photoluminescence becomes less efficient until it disappears for p=5.0 mm Hg. This study shows that CSVT-GaAs epilayers grown under proper conditions have high quality and could be used for producing some electronic devices.