Deep-level transient spectroscopy study of narrow SiGe quantum wells with high Ge content

Abstract

We present a detailed theoretical and experimental study of hole emission processes in p-type Si/SiGe/Si structures under the nonequilibrium conditions found in deep-level transient spectroscopy ͑DLTS͒ investigations. We clarify the possibilities and limitations of DLTS applied to quantum-well ͑QW͒ structures. We report an observation of the effect of thermally activated tunneling induced by local high electric field on the emission rate of confined holes. In the limit of high external electric field F, the hole emission rate e T increases with F according to e T ϭe T ͑0͒exp(F 2 /F c 2 ), where the characteristic field F c agrees with theoretical calculations. The effect of nonequilibrium carrier diffusion is determined from the dependence of the DLTS signal on the pulse frequency, allowing one to estimate the effective hole diffusion coefficient. Interface roughness scattering, which controls the carrier mobility in the narrow QW, is investigated. The observed diffusion coefficient depends only slightly on the width for the investigated narrow SiGe QW's ͑2-3 nm͒, but depends strongly on the Ge content ͑xϭ0.3-0.5͒ in agreement with theory. A strong increase of the hole emission activation energy with decreasing nonequilibrium hole concentration gives evidence for considerable fluctuations of lateral potential, inducing lateral localization of confined holes at low temperatures. We show that interface roughness is responsible for these lateral potential fluctuations. ͓S0163-1829͑96͒08248-3͔

Interface roughness effect on density of states and mobility of narrow Si/Si1−xGexquantum wells: path-integral approach

“…For the wide QW with a 4.5 nm, the RMS of the fluctuation potential in figure 1 is very weak, consistent with a previous study [38]. As a consequence, the tailing effect in the DOS in figure 3 is also very weak.…”

<title>Surface scattering in thin films: wave guide strategy</title>

“…However, we argue that under the condition (6) for smooth roughness obeying the condition (5). This result is well known (see, for instance, [22]). It could be simply deduced with the assumption of an effective scattering potential resulting from film thickness variations.…”

“…The second limit is kl >> 1 (22) When it is valid scattering significantly depends upon angle 8 because only small transient vectors q much less than kE are possible. In this case occurs small-angle scattering to the nearest subbands.…”

Electrical characterization of silicon wafer bonding interfaces by means of voltage dependent light beam and electron beam induced current and capacitance of Schottky diodes

“…While no considerable effect of illumination was detected at 300 K, a considerable increasing of sample capacitance under illumination was observed at low temperature 80 K. This result can be understood assuming the presence of depletion region along the bonded interface induced by DN barrier. At room temperature the over-barrier current can but at 80 K cannot follow the capacitance testing 1 MHz signal, as it was previously reported for analogous structure with quantum well inside [8].…”