Effect of free-carrier concentration and optical injection on carrier lifetimes in undoped and iodine doped CdMgTe/CdSeTe double heterostructures grown by molecular beam epitaxy

• Published in: Journal of physics. D, Applied physics Applied physics, 2016-11, Vol.49 (50), p.505104
• Main Authors: Sohal, S, Edirisooriya, M, Ogedengbe, O S, Petersen, J E, Swartz, C H, LeBlanc, E G, Myers, T H, Li, J V, Holtz, M
• Format: Article
• Language: English
• Subjects: CdTe; heterostructures; lifetime; photoluminescence
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/49/50/505104

Time-resolved and time integrated photoluminescence (PL) studies are reported for undoped and doped CdMgTe/CdSeTe double heterostructures (DHs) grown by molecular beam epitaxy. Undoped DHs are studied with absorber layer thickness varying from 0.5 to 2.5 µm. The n-type free-carrier concentration is varied ~7  ×  1015, 8.4  ×  1016, and 8.4  ×  1017 cm−3 using iodine as a dopant in different absorber layer thicknesses (0.25-2.0 µm). Optical injection is varied from 1  ×  1010 to 3  ×  1011 photons/pulse/cm2, corresponding to the initial injection of photo-carriers up to ~8  ×  1015 cm−3, to examine the effects of excess carrier concentration on the PL lifetimes. Undoped DHs exhibit an initial rapid decay followed by a slower dependence with carrier lifetimes up to ~485 ns. The dependence of carrier lifetimes on the thickness of the absorber layers (0.5-2.5 µm) suggests interface recombination velocities (vint ) ~ 1288 and 238 cm s−1 in the initial and later decay times, respectively, corresponding to high and low photo-carrier concentrations. The Shockley-Read-Hall model is used to describe the results in which variations are observed in vint  for undoped DHs. The lifetimes of doped DHs show a consistent trend with thickness. The vint  ~ 80-200 cm s−1 is estimated for doping n ~ 7  ×  1015 cm−3 and 240-410 cm s−1 for n ~ 8.4  ×  1016 cm−3. The observed decrease in carrier lifetimes with increasing n is consistent with growing importance of the radiative recombination rate due to the excess carrier concentration. The effect of carrier concentration on the PL spectrum is also discussed.