Reliable contacts to two-dimensional conduction layers

For many experiments and device applications, electrical contacts to a two-dimensional conduction layer must remain reliable under repeated temperature cycling between 300 and 77 K or lower. This work introduces the use of a silicon-doped InAs contact to the AlGaAs/GaAs two-dimensional electron gas which demonstrates exceptional reliability under such temperature cycling. The noise spectrum of AlGaAs/GaAs contacted with silicon-doped InAs shows almost no dependence on bias current; this fact can be used to improve the performance of device applications such as Hall sensors. In addition, this work introduces an alternative two-dimensional conduction structure, highly mismatched InAs/GaP. InAs/GaP contacted with Ti/Au shows reliability equal to AlGaAs/GaAs contacted with silicon-doped InAs. The InAs/GaP material may be more desirable for some applications because of the lower temperature dependence of its electronic properties and potentially easier integration with silicon-based microelectronics. (C) 2000 American Institute of Physics. [S0003-6951(00)04822-1].