Accurate measurement of composition, carrier concentration, and photoconductive lifetime in Hg1−xCdxTe grown by molecular beam epitaxy

Abstract

Variable magnetic field Hall and transient photoconductance lifetime measurements were performed on a series of undoped, In-doped, and As-doped HgCdTe samples grown by molecular beam epitaxy and metalorganic chemical vapor deposition. Temperature variation and, in the case of Hall, magnetic-field variation are needed to give a more complete picture of the mechanisms that control lifetimes in HgCdTe samples. Recent predictions of recombination lifetimes from full band structure calculations were compared to experimental lifetimes at various doping levels at long-wave infrared (LWIR) and mid-wave infrared (MWIR) compositions. For n-type material, lifetimes from low doping levels fall well below the predictions, implying that Shockley-Read-Hall (SRH) recombination is still dominant. MWIR samples have a lifetime that increases somewhat with carrier concentration, suggesting that In doping passivates the SRH defects for that composition. Lifetimes in p-type MWIR material appear to be well-explained by recent theoretical calculations. In p-type material, trapping states may be introduced during the incorporation and activation of As, since some samples with unusually long lifetimes had a distinctly different type of temperature dependence.

Numerical Modeling of IR-Laser-Irradiated HgCdTe

“…3 all show a reduced downward slope of the lifetime at high excess carrier densities, and it is suspected that this is due to nonintrinsic mechanisms such as defect or surface recombination. [7][8][9] Lifetimes in corresponding defect-free bulk material are therefore expected to be somewhat longer. The lifetime used in the simulations does not quite fulfil the latter criterion, but the results in Ref.…”

“…Uncertainties regarding Auger lifetimes [4][5][6][7][8][9][10][11][12][13][14][15][16] have been much debated lately. [4][5][6][7][8][9] Considering the large spread in reported experimental Auger lifetimes in the literature, it would appear that extrinsic (impurity and surface) recombination may have played a role in cases previously thought to be solely controlled by Auger mechanisms.…”

“…[4][5][6][7][8][9] Considering the large spread in reported experimental Auger lifetimes in the literature, it would appear that extrinsic (impurity and surface) recombination may have played a role in cases previously thought to be solely controlled by Auger mechanisms. Indeed, recent theoretical calculations 4-6 have given much longer Auger lifetimes than those predicted by conventional expressions, [13][14][15][16] and the model has been adjusted to take this into account.…”