IN0.53GA0.47AS METAL-SEMICONDUCTOR-METAL PHOTODIODES WITH TRANSPARENTCADMIUM TIN OXIDE SCHOTTKY CONTACTS

A metal-semiconductor-metal (MSM) In0.53Ga0.47As photodiode using a tr ansparent cadmium tin oxide (CTO) layer for the interdigitated electro des was investigated. The transparent contact prevents shadowing of th e active layer by the electrodes, thus allowing greater collection of incident light. The barrier height (phiBn) of CTO on i-In0.52Al0.48As was determined to be 0.47 eV, while the Ti/Au barrier height was 0.595 eV. The reduced barrier height for CTO is caused by tunneling through the sputter-damaged cap layer. Responsivity for 1.3 mum incident ligh t was 0.49 and 0.28 A/W, respectively, for the CTO and Ti/Au MSM photo diodes. No antireflection (AR) coating was utilized over the bare semi conductor surface. The CTO MSM photodiode shows a factor of almost two improvement in responsivity over conventional Ti/Au MSM photodiodes. (C) 1994 American Institute of Physics.