Quantum point contacts on InGaAs/InP heterostructures

✍ Scribed by G. Engels; M. Tietze; J. Appenzeller; M. Hollfelder; Th. Schäpers; H. Lüth

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 73 KB
• Volume: 23
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1006/spmi.1996.0588

✦ Synopsis

For the first time we have observed quantized conductance in a split gate quantum point contact prepared in a strained In 0.77 Ga 0.23 As/InP two-dimensional electron gas (2DEG). Although quantization effects in gated two-dimensional semiconductor structures are theoretically well known and proven in various experiments on AlGaAs/GaAs and also on In 0.04 Ga 0.96 As/GaAs, no quantum point contact has been presented in the InGaAs/InP material with an indium fraction as high as 77% so far. The major problem is the comparatively low Schottky barrier of the InGaAs (φ B ≈ 0.2 eV) making leakage-free gate structures difficult to obtain. Nevertheless this heterostructure-especially with the highest possible indium content-has remarkable properties concerning quantum interference devices and semiconductor/superconductor hybrid devices because of its large phase coherence length and the small depletion zone, respectively. In order to produce leakage-free split gate point contacts the samples were covered with an insulating SiO 2 layer prior to metal deposition. The gate geometry was defined by electron-beam lithography. In this paper we present first measurements of a point contact on an In 0.77 Ga 0.23 As/InP 2DEG clearly showing quantized conductance.