Ballistic transport in InSb quantum wells at high temperature

Suppression of the parasitic buffer layer conductance in InSb/AlxIn1−xSb heterostructures using a wide-band-gap barrier layer

“…At sufficiently low temperatures, the Al 0. 15 In 0.85 Sb buffer layer is depleted. However, dependent on the doping density of the δ-doped region, the Al 0.2 In 0.8 Sb top cap layer can be occupied and even degenerate, presenting a low-mobility conducting channel in parallel to the high-mobility InSb 2DEG.…”

“…Due to the nature of the heterostructure, the three layers are spatially separated, but the Al 0.2 In 0.8 Sb layer, the InSb 2DEG, and the top of the Al 0. 15 In 0.85 Sb buffer layer are in intimate contact through the shallow Ohmic contacts. The three layers can therefore be considered to experience the same local electric field, unlike an isolated layer model 25 (this is also reasonable due to the lateral dimensions of the device).…”

“…In this elevated temperature regime, we now consider the additional conduction in the Al 0. 15 In 0. 85 Sb buffer layer and analyze our data using a three-carrier model accordingly.…”

“…46 The calculated electron sheet densities in the 3-μm-thick Al 0. 15 In 0.85 Sb layer (SBL) and the isolated 300-nm Al 0. 15 In 0.85 Sb layer of the MBL samples are shown in Fig.…”

“…Reports of ballistic transport in mesoscopic InSb/Al x In 1-x Sb devices have, however, been limited to T 205 K due to poor electrical isolation of the 2DEG rather than size arguments. 15 Quasi-1D narrow channels are typically formed by shallow mesa-etching 15,16 or surface gates 17,18 to confine the 2DEG. Both techniques have proved successful for InSb/Al x In 1-x Sb structures at low temperatures, but unacceptable gate leakage prohibits the use of the latter at temperatures much greater than 10 K. 17 For shallow mesa-etched channels, the surrounding Al x In 1-x Sb buffer layer becomes electrically significant at temperatures > 150 K, and the parallel conduction reduces the measured ballistic component from the 2DEG to the extent where it is no longer well defined.…”