Scattering mechanisms affecting hole transport in remote-doped Si/SiGe heterostructures

Abstract

Boron modulation-doped Si/SiGe heterojunctions have been grown by molecular beam epitaxy. The two-dimensional hole gas formed along the heterojunction, just inside the alloy, has a sheet density in the range 2–5×1011 cm−2 and a typical mobility at 5 K of 2000 cm2 V−1 s−1. An explanation for the magnitude of the mobility is sought by considering likely scattering mechanisms, namely those due to remote impurities, interface roughness, alloy disorder, and interface impurities. A self-consistent model is used to determine the sheet density in terms of structural and energy parameters and dopant concentrations in the heterostructure. It is shown that the presence of negatively charged impurities at the heterojunction provides the basis for a consistent interpretation of the experimental results.

Partially Suppressed Shot Noise in Hopping Conduction: Observation in SiGe Quantum Wells

“…(3). This estimation of the localization radius is consistent with a fluctuation potential created by interface impurities separated about 200 Å from each other (surface density of 2 3 10 11 cm 22 [20]) and validates our low-field assumption since for V sd 30 mV (inset, Fig. 2) it is Ea Ӎ 0.15 , k B T ͞e Ӎ 0.36 meV.…”

Silicon-germanium heterostructures ? advanced materials and devices for silicon technology

“…At Warwick record mobilities of 19 800 cm / V-1 s-1 at 7 K in a Sio.93Ge0.07 channel, four times greater than previously reported [26], and l ll00cm / V -1 s -1 at 4 K in a Sio.sTGeo.13 channel have been obtained, limited by interface charge scattering. Theoretical estimates [26,27] place the 4 K alloy scattering limited mobility for x = 0.1 at 30 000 cm 2 V-1 s-1, for a carrier sheet density of 1 x 1012 cm -2. In contrast, the highest mobility reported for the Sip MOS inversion layer is only 2 500 cm 2 V-1 s-1 (at 4 K), in a structure grown on a (110) substrate which is not preferred for device applications [28].…”

Low temperature hole mobility in strained p-Si/Si1−xGex/p-Si selectively doped double heterojunctions

“…Kundu et al [7] presented mobility calculations using a new wavefunction which is a trigonometric function inside the well and decays exponentially in the barrier (Si layer). Mobility calculations have been also performed using Fung-Howard-type wavefunctions [2,8].…”