“Cold” Tunneling Ohmic Contact With p-GaAs Nanolayer 10 nm Thick

To elucidate the possibility of creating an ohmic contact with an extremely thin p-GaAs nanolayer, we have studied the properties of the contact deposited without annealing (“cold” contact) with a p-layer $\sim $ 8 nm thick formed on the n-GaAs wafer by low-energy Ar $^{+}$ ions due to the conductivity type conversion (n $\to $ p). Exclusion of annealing prevents metallization of the semiconductor nanolayer. Despite the obvious formation of the Schottky barrier and the presence of a residual oxide layer, the current–voltage characteristics of the ion-induced p-n structure indicates the ohmic nature of the contact. It is shown that high concentration of defects in the irradiated p-layer leads to a decrease in the barrier width down to the value ${W}$ = 0.3 nm, which is much smaller than the de Broglie wavelength of p-layer charge carriers ( $\lambda >$ 2–19 nm). Therefore, the ohmic character of the contact is provided by holes and electrons of the p-layer tunneling through the barrier. It is shown that the “cold” tunneling ohmic contact on p-GaAs can be formed with any metal if a defect or doping density is ${N}_{\text {D}} > 10^{20}$ cm $^{-{3}}$ , which is an order of magnitude higher than the value ( ${N}_{\text {D}} > 10^{19}$ cm $^{-{3}}{)}$ considered as providing efficient tunneling of carriers through a contact with heavily doped n-type semiconductors.