High performance Hall -sensor devices based on III-V heterojunction contacts and materials

The AlGaAs/GaAs based 2-Dimensional Electron Gas (2DEG) structure has long been known as the ideal structure for high sensitivity Hall-sensor devices due to the high electron mobility, low sheet carrier concentration, and well-confined conducting channel. However, the lack of temperature-cycling reliability has greatly hampered its large scale industrial application. Exploratory work has been carried out to solve this problem in two different ways. One is by utilizing a new non-alloyed contact scheme to achieve a better and more stable contact to the 2DEG structure. Another way is to study totally new material system. We have chosen the highly mismatched InAs/GaP heterostructure, which is much easier to make ohmic contact with, and also promises less temperature sensitivity. Initial results show that the contact performance is significantly improved by using a heavily Si doped InAs layer on top of AlGaAs/GaAs 2DEG structure and the sensitivity figure-of-merit was increased by more than 8% at low temperatures. Most importantly, the reliability is greatly improved under temperature cycling from 5–300K. Although the sensitivity of preliminary InAs/GaP Hall sensors is somewhat lower than that of the 2DEG devices, due to the higher sheet carrier concentration within the InAs layer, the sensitivity vs. temperature dependency of the InAs/GaP sample is much lower (better!) than that of the 2DEG structure between 5 and 300K. Device reliability test shows that the InAs/GaP Hall sensor is very stable under temperature cycling between 77–300K. Magnetic field resolution in the order of 10 −7∼10−8T/[special characters omitted] has been achieved on all the three types of Hall sensors, which are 3∼4 orders of magnitude better than ordinary Hall sensors, and is comparable to that of SQUID magnetometer.