Characterization of InSb quantum wells with atomic layer deposited gate dielectrics

Abstract

We report magnetotransport measurements of a gated InSb quantum well (QW) with high quality Al 2 O 3 dielectrics (40 nm thick) grown by atomic layer deposition. The magnetoresistance data demonstrate a parallel conduction channel in the sample at zero gate voltage (V g ). A good interface between Al 2 O 3 and the top InSb layer ensures that the parallel channel is depleted at negative V g and the density of twodimensional electrons in the QW is tuned by V g with a large ratio of 6.5 × 10 14 m -2 V -1 but saturates at large negative V g . These findings are closely related to layer structures of the QW as suggested by self-consistent Schrödinger-Poisson simulation and two-carrier model.

Gate depletion of an InSb two-dimensional electron gas

“…Based on a self-consistent Schr€ odinger-Poisson (SP) simulation, we predicted that the 2DEG would be depleted in an InSb QW with a wider-band-gap Al x In 1Àx Sb surface layer that is expected to prevent the hole accumulation. 11 In this letter, we show experimental evidence that the 2DEG in an InSb QW with an Al 0.1 In 0.9 Sb surface layer (sample 2) is completely depleted. Particularly noteworthy is that the Al 0.1 In 0.9 Sb layer also has the advantages of suppressing a parallel conduction channel and of keeping a relatively low interface trap density in the depletion process as revealed by our modified SP simulation.…”

“…3,8 More recently, we have grown a high quality Al 2 O 3 gate dielectric on an InSb QW structure with an InSb surface layer (hereafter referred to as "sample 1") using atomic layer deposition (ALD). 11 The Fermi level of this sample is tuned almost entirely across the band gap of InSb via gate bias. The good interface between the Al 2 O 3 and InSb layers makes this possible, and allows us to study the importance of the layer sequence in gate controllability.…”

“…After a Hall bar mesa (80 lm  30 lm) was defined by photolithography, a 40-nm-thick Al 2 O 3 layer was deposited using ALD at 130 C without any surface treatment 12 (details of the ALD growth and the epitaxial layer structure are described in Ref. 11). The lower panel of Fig.…”

“…Figure 1(a) shows the energy band diagram (up to 85 nm in depth) of sample 2 at zero gate bias (V g ) calculated from the SP simulation with a Schottky barrier model. 11,13 In this SP simulation, a unique fitting parameter is the Schottky barrier height / B that is determined by properties of the semiconductor surface and interface states. The energy difference between the conduction band (CB) minimum E c at zero depth and the Fermi energy E F (set at 0 eV) corresponds to / B , which can be adjusted manually for agreement between the simulated and the measured 2DEG density n s .…”

Design and Performance Analysis of Depletion-Mode InSb Quantum-Well Field-Effect Transistor for Logic Applications

“…1 shows the cross-sectional view of an InSb QWFET structure with a 10 nm-thick Al 2 O 3 gate insulator, which has been optimized for high electron mobility and a small V p . The buffer layer of the device consists of a 3µm insulator have been presented elsewhere [10,11].…”