Ambipolar diffusion in strained Si1−xGex(100) layers grown by molecular beam epitaxy

Abstract

Carrier dynamics in strained Si1−xGex layers and Si/Si1−xGex superlattices, grown by molecular beam epitaxy with different Ge concentrations, were investigated by a transient grating method. The ambipolar diffusion coefficient Da of carrier transport parallel to the layer plane was determined at high-density carrier excitation. An increase to Da values by a factor of up to 1.5 was observed for the strained alloy films compared to the value for moderately doped molecular beam epitaxy silicon layers. This is the first experimental evidence for enhanced performance of parallel carrier transport in Si1−xGex alloy layers.

Time-resolved measurements of charge carrier dynamics in Mwir to Lwir InAs/InAsSb superlattices

“…Measurement of the in-plane transport in the Ga-free InAs/InAsSb T2SLs is of interest due to their relatively light in-plane heavy-hole mass, which should lead to an enhancement of the in-plane transport. Here, the influence of SL period thickness on carrier transport is studied using a photo-generated transient-grating technique [52][53][54][55][56]. This technique can provide a direct measure of the ambipolar diffusion coefficient in InAs/InAs 0.85 Sb 0.15 T2SLs.…”

“…Photo-generated transient-grating experiments have been performed for various semiconductors such as Ge [51], GaAs/AlGaAs quantum wells, SiGe alloys [52], Si [53], InSb [54], and InAs/GaAs SLs [55,56]. Measurement of the in-plane transport in Ga-free MWIR InAs/InAsSb T2SLs is of interest due to their relatively light in-plane heavy-hole mass, which should lead to an enhancement of the in-plane transport.…”

“…In Chapter 4, the thicker SL period sample (L SL =393Å) was shown to have a factor of two longer MC lifetime than the thin SL layer samples (L SL =147Å and L SL =197Å) at 77 K. The samples GN0835, GN0837, and GN0838 are studied here to assess the quality of the SL structure and estimate the influence of SL period thickness on carrier mobility. To achieve this goal, photo-generated transient-grating experiments are performed to provide a direct measure of in-plane carrier transport properties in InAs/InAs 0.85 Sb 0.15 [52][53][54][55][56]. In this chapter, a brief discussion of this approach and experimental results of the study are presented.…”