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

• Externally doping a semiconductor damages the lattice and increases recombination. • Surface carrier concentration can be increased by depositing a charged thin film. • Thin film induced carriers can be used to realize a dopant free ohmic contact. • Opening a charged thin film causes carriers to drift under the opening. • Contact resistivity of 0.24 mΩcm 2 was achieved with thin film induced contacts. 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) Al 2 O 3 thin film. The idea is to utilize the negative charge of ALD Al 2 O 3 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 Al 2 O 3 induced contacts are not only ohmic, but also have a low contact resistivity of 0.24 mΩ⋅cm 2 . This matches the requirements of various electron devices such as photodiodes indicating potential for the proposed contact formation method.