Local two-dimensional electron gas formation in p-doped GaAs/InyGa1−yAs/AlxGa1−xAs heterostructures by focused Si-implantation doping

Abstract

To investigate the possibility of fabricating two-dimensional bipolar devices by focused ion implantation doping, selectively p-doped GaAs/InyGa1−yAs/AlxGa1−xAs heterostructures containing a two-dimensional hole gas (2DHG) were implanted with Si to overcompensate the p-doping locally and create a laterally structured two-dimensional electron gas (2DEG). In this way, a two-dimensional p–n junction can be formed. The p-doped base material had a hole concentration of p = 5.4 × 1011 cm−2 and a hole mobility of 240 cm2 V−1 s−1. Si was implanted with 60 keV at doses from 2 × 1012 cm−2 to 2 × 1013 cm−2, using a focused ion beam system. Up to implantation doses of 1 × 1013 cm−2, the formation of a 2DEG without unwanted parallel conducting channel was observed. For higher implanted doses additional three-dimensional conduction is observed. The highest electron concentration obtained without parallel conduction was 5 × 1011 cm−2 at 300 K as well as at 4.2 K. The corresponding mobilities are 5000 cm2 V−1 s−1 at room temperature and 6000 cm2 V−1 s−1 at 4.2 K. A first two-dimensional p–n junction fabricated by this method showed good I–V characteristic of a diode.