P-I-N photodiodes with transparent conductive contacts

US5212395A · kind A · utility

Assignee

• AT&T Bell Laboratories · US

Inventors

• Paul R. Berger · Summit, US
• Alfred Yi Cho · Summit, US
• Niloy K. Dutta · Colonia, US
• John E. Lopata · Naperville, US
• Henry M. O'Bryan, Jr. · Plainfield, US
• Deborah Lee Sivco · Hackettstown, US
• George J. Zydzik · Columbia, US

Key dates

• Filing date: Mar 2, 1992
• Grant date: May 18, 1993
• Expiry date: Mar 2, 2012

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10F77/306

Abstract

This invention pertains to a p-i-n In.sub.0.53 Ga.sub.0.47 As photodiode having an optically transparent composite top electrode consisting of a thin semitransparent metal layer from 10 to 40 nm thick and a transparent cadmium tin oxide (CTO) layer from 90 to 600 nm thick. The metal layer makes a non-alloyed ohmic contact to the semiconductor surface, acts as a barrier between the semiconductor and the CTO preventing oxidation of the semiconductor from the O.sub.2 in the plasma during reactive magnetron sputtering of the CTO layer, and prevents formation of a p-n junction between the semiconductor and CTO. The CTO functions as the n or p contact, an optical window and an anti-reflection coating. The top electrode also avoids shadowing of the active layer by the top electrode, thus allowing greater collection of incident light. Since the top electrode is non-alloyed, inter-diffusion into the i-region is not relevant, which avoids an increased dark current.