Charged thin film enables dopant free ohmic metal–semiconductor contact formation

Ohmic contacts are conventionally achieved by externally doping the surface of a semiconductor substrate underneath a metal contact. To avoid the inconveniences that come with heavy doping, we propose an alternative way of achieving an ohmic Al-Si contact utilizing a highly charged atomic layer deposited (ALD) Al2O3 thin film. The idea is to utilize the negative charge of ALD Al2O3 to attract holes towards the surface of the Si substrate and thereby induce a p + region and consequently an Al/p + Si contact. The results show that the Al2O3 induced contacts are not only ohmic, but also have a low contact resistivity of 0.24 mΩ⋅cm2. This matches the requirements of various electron devices such as photodiodes indicating potential for the proposed contact formation method.