Identification of dislocations in n-type heterostructures by deep-level transient spectroscopy

Abstract

Plastic relaxation of Si 1−x Ge x layers on (100) Si leads to formation of misfit dislocations at the heterointerface and threading dislocations through the heterostructure. We report here a deep-level transient spectroscopy (DLTS) investigation of dislocations in n-type Si/Si 0.88 Ge 0.12 /Si heterostructures grown by selective epitaxy using low-pressure chemical vapour deposition (LPCVD). DLTS was used to detect deep states correlated with dislocations. Measurements were performed on large-area samples (relaxation degree of 63%) as well as on small areas (relaxation degree of 4%) grown selectively on the same wafer. The bias-dependent DLTS peak heights are consistent with a spatially varying dislocation density. This variation, and the combined interpretation of the corresponding DLTS peaks from large and small areas, allowed us to associate one of the deep levels with misfit dislocations at the heterointerface, a second one with threading dislocations and the third one with defects present in the SiGe layer near the interface.

Effect of interface states on population of quantum wells in SiGe/Si structures

“…Typical background concentration of holes in Si 1-x Ge x /Si heterostructures for majority of developed applications is higher than 10 16 cm -3 (for example, see [4,5]). Typical concentration of defectrelated deep levels in MBE-grown thin Si 1-x Ge x /Si heterostructures or silicon is ~ 10 14 -10 15 cm -3 , and density of the interface traps is ~10 10 -10 12 cm -2 [6][7][8]. Decreasing background impurity concentration down to 10 15 cm -3 and selective doping in the density range of 10 11 -10 12 cm -2 makes a Si 1-x Ge x /Si heterostructures very sensitive to the presence of deep levels and interface traps.…”

Electrical and photovoltaic properties of CdTe/ZnTe n-i-p junctions grown by molecular beam epitaxy

“…Such behavior is characteristic for extended defects, which include dislocations or other sources with continuous distributions of states. The broadened DLTS peaks associated with dislocations were observed in many other semiconductor structures, e.g., in: SiGe, 13,14 InGaAs, 15,16 and GaAsSb. 17,18 Thus, the broad contribution in the case of investigated samples can have its origin in the extended defects present in the i-CdTe material.…”

Photoelectric transient process in Si1-xGex/Si superlattices

“…Lifetimes of the LE, BE and FE have already been investigated by the time-resolved PL technique [1,2,8,9]. Deep level states related to dislocations were also observed in steady state PL and deep level transient spectroscopy (DLTS) [10,11]. Nonradiative pathways were noticed to play important roles in Si 1−x Ge x /Si SLs [12,13] and the transportation of nonequilibrium carriers, via tunnelling, thermal diffusion and drift by electric field, also strongly affects the transient process in the SLs [14][15][16][17][18].…”