Electrical and optical properties of undoped GaSb grown by molecular beam epitaxy using cracked Sb1 and Sb2
1999; Elsevier BV; Volume: 207; Issue: 4 Linguagem: Inglês
10.1016/s0022-0248(99)00379-6
ISSN1873-5002
AutoresQianghua Xie, J. E. Van Nostrand, Robert Jones, J. R. Sizelove, D. C. Look,
Tópico(s)Chalcogenide Semiconductor Thin Films
ResumoIn this paper, we report on the electrical and optical properties of undoped GaSb samples grown by MBE using Sb1 as well as Sb2 produced in a conventional antimony cracker. We establish the existence of Sb1 and then extract the mole fraction of Sb1 in the antimony beam as a function of the cracking zone temperature based on a combined analysis of mass spectrometry data and ion gauge flux reading. We find that the Sb1 mole fraction becomes greater than 90% for cracking zone temperature above 950°C. A series of undoped GaSb samples are grown over a wide range of substrate temperature, V/III ratio and cracking zone temperature. The undoped GaSb samples grown at 550°C show p-type conductivity with a room-temperature hole mobility and hole concentration of ∼730 cm2 v−1 s−1 and ∼3×1016 cm−3, respectively. The hole mobility and hole concentration are essentially independent of the V/III ratio over a range of 1.2–4. Decreasing the growth temperature to 440°C leads to a simultaneous decrease in hole mobility, residual hole concentration and photoluminescence intensity. Hole mobility and hole concentration do not depend strongly on the cracking zone temperature in the range 790–1000°C; however, the optical intensity of the samples grown using Sb1 is approximately one order of magnitude stronger than those using Sb2. Besides the commonly seen bound exciton transitions at 805 (BE1), 803 (BE2), 800 (BE3) and 796 meV (BE4), a free exciton transition at ∼809.4 meV (4 K) is observed in the samples grown with Sb1 at 550°C, indicating a greatly reduced density of nonradiative recombination centers.
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