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

To investigate the possibility of fabricating two-dimensional bipolar devices by focused ion implantation doping, selectively p-doped GaAs/In y Ga 1− y As/Al x Ga 1− x As 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 × 10 11 cm −2 and a hole mobility of 240 cm 2 V −1 s −1 . Si was implanted with 60 keV at doses from 2 × 10 12 cm −2 to 2 × 10 13 cm −2 , using a focused ion beam system. Up to implantation doses of 1 × 10 13 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 × 10 11 cm −2 at 300 K as well as at 4.2 K. The corresponding mobilities are 5000 cm 2 V −1 s −1 at room temperature and 6000 cm 2 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.