Nonalloyed transparent ohmic contact of indium tin oxide to p-type Si0.8Ge0.2

Nonalloyed transparent ohmic contacts of indium tin oxide (ITO) to p-type Si0.8Ge0.2 layer with and without a Si-capping layer were examined. The ITO films and the p-type Si0.8Ge0.2 layers were deposited by using sputtering and ultrahigh-vacuum chemical vapor deposition, respectively. It is shown that the ITO/p-type Si0.8Ge0.2 contact structure exhibits a specific contact resistance of 2.26 × 10− 5 Ω cm2 as compared to that of 2.78 × 10− 2 Ω cm2 for the ITO/Si/p-type Si0.8Ge0.2 contact structure. Possible mechanisms are proposed. The ITO film exhibits a transmittance more than 85% within a wavelength range from 800 to 1400 nm. Therefore, the ITO film has a high potential for fabricating near infrared optoelectronic devices using Si1−xGex material.