Role of Dislocation Scattering on the Electron Mobility of n-Type Long Wave Length Infrared HgCdTe on Silicon

Abstract

It has been reported that the basic electrical properties of n-type long wave length infrared (LWIR) HgCdTe grown on silicon, including the majority carrier mobility (l e ) and minority carrier lifetime (s), are qualitatively comparable to those reported for LWIR HgCdTe grown on bulk CdZnTe by molecular beam epitaxy (MBE). Detailed measurements of the majority carrier mobility have revealed important differences between the values measured for HgCdTe grown on bulk CdZnTe and those measured for HgCdTe grown on buffered silicon substrates. The mobility of LWIR HgCdTe grown on buffered silicon by MBE is reported over a large temperature range and is analyzed in terms of standard electron scattering mechanisms. The role of dislocation scattering is addressed for high dislocation density HgCdTe grown on lattice-mismatched silicon. Differences between the low temperature mobility data of HgCdTe grown on bulk CdZnTe and HgCdTe grown on silicon are partially explained in terms of the dislocation scattering contribution to the total mobility.

Recent Progress in MBE Growth of CdTe and HgCdTe on (211)B GaAs Substrates

“…1 Teledyne Imaging Sensors (TIS) (formerly Rockwell) has helped pioneer the development of alternate substrates. 1,[3][4][5][6][7] Early developmental work by Arias et al on GaAs substrates proved that relatively high-quality HgCdTe could be grown on lattice-mismatch systems. 2 GaAs substrates were eventually abandoned for the lattice-and CTE-matched bulk CdZnTe substrates; however, the feasibility of using an alternate to bulk CdZnTe was established.…”

“…This is consistent with reported HgCdTe dislocation densities for growth on all alternate substrates as being significantly higher than for HgCdTe grown on bulk CdZnTe. 1,[3][4][5][6][7] Perhaps even more significant than the large lattice mismatch is the CTE mismatch between the HgCdTe and the alternate substrate of choice. The CTE mismatch between HgCdTe and Si is dramatic, while the CTE mismatch between HgCdTe and GaAs or Ge is significantly less.…”

Electrical properties of HgCdTe films grown by MOCVD and doped with as

“…Therefore, sample 3 at 77 K could be regarded as having n−type conductivity, though a substantial contribution of holes was seen. The mobility of high−mobility electrons at T = 77 K (μ nhm = 48800 cm 2 V -1 s -1 ) in sample 3 was much lower than the maximum possible value of mobility in MCT with x = 0.188, which approaches 250000 cm 2 V -1 s -1 [14]. Though a certain degree of scattering by structural defects could be assumed, still it could be suggested that this sample was heavily electrically compensated.…”

Dislocation Reduction of HgCdTe/Si Through Ex Situ Annealing

“…[1][2][3][4][5][6][7][8] However, the goal of advancing this material technology to the long-wavelength (LWIR) regime has been hampered by the one to two orders of magnitude increase in dislocation density with respect to HgCdTe grown on lattice-matched bulk CdZnTe substrates. This deficiency in dislocation density has been shown to limit lifetimes, 9,10 lower mobility of carriers, 11 lead to larger dark currents in longwavelength detectors, 12,13 and ultimately reduce focal-plane array operability. 9,14 Current growth methods of HgCdTe/Si result in a dislocation density of mid 10 6 cm À2 to low 10 7 cm À2 .…”