Ohmic Contact Properties of Magnesium Evaporated onto Undoped and P-doped a-Si: H

Abstract

We have investigated the current-voltage characteristics of metal/undoped a-Si: H/n + (or p +) c-Si structures using Mg, Au, Pt and Al. It has been indicated that the energy band of undoped a-Si: H shows a downward bending against Mg, being analogous to n + a-Si: H/undoped a-Si: H contact, while the band shows an upward bending against Au, Pt and Al. Mg/undoped a-Si: H contact is found to allow injection of electrons into the conduction band of a-Si: H, providing us a good ohmic contact property. This contact does not exhibit the thermal-degradation at least up to 100°C.

Erbium electroluminescence in forward‐biased amorphous silicon p‐i‐n diodes

“…In the course of the study we found that the n + layer could be omitted if in place of chromium magnesium was evaporated as the top contact. These p-i-Mg structures have exhibited more reliably high forward currents than the p-i-n-Cr structures in accordance with the observation that Mg forms ohmic contacts with n-type a-Si:H films [10]. For comparison we also fabricated plain p-n diodes.…”

n+-Doped-layer free amorphous silicon thin film solar cells fabricated with the CuMg alloy as back contact metal

“…was due to the lower shunt resistance and higher series resistance. As previously report, the ohmic behavior is observed for metals having work function (Um) lower than the electronic affinity (v s ) of the Si film (v s $ 4.0 ± 0.1 eV) [17,18]. Because the work function Um of Mg was 3.46 eV, the Mg was easily to form the ohmic contact with a-Si:H layer.…”

“…3 is 2.22 Â 10 À5 A and À3.50 Â 10 À8 A. According to the previous report [17], the insufficient ohmic contact may also result from the defects at the interface between the a-Si:H and metal. In addition to the increase of dark leakage current, the large interface defects also increased the electron-hole pair recombination probability and resulted in the lower V oc and J sc .…”

The influence of ohmic back contacts on the properties of a-Si:H Schottky diodes

“…In general a thin n + a-Si:H layer is sandwiched between the metal and a-Si:H layers to make the contact ohmic [1]. But this process is an extra undesired step therefore electrical properties of variety of metal/ a-Si:H ohmic contacts were investigated by researchers [2,3]. For example, Sb is sandwiched between the metal and a-Si:H as a thin layer instead of n + a-Si:H layer [4].…”

“…Because of high electron density of Sb, it behaves like n + layer. Although Matsuura [2] claims that Mg is the best metal for making ohmic contact to a-Si:H. In general Al or Cr is used for making ohmic contacts to a-Si:H.…”