Metal-semiconductor-metal (MSM) photodiodes with an In0.53Ga0.47As active region were investigated using a transparent cadmium tin oxide (CTO) layer for the interdigitated electrodes to improve the low responsivity of conventional MSM photodiodes with opaque electrodes. CTO is suitable as a Schottky contact an optical window and an anti-reflection (AR) coating. The transparent contact prevents shadowing of the active layer by the top electrode thus allowing greater collection of incident light. Responsivity of CTO-based MSM photodiodes with 1-μm finger widths and 2-μm finger spacings and without an AR coating between the electrodes was twice (0.62 A/W) that of a similar MSM photodiodes with Ti/Au electrodes (0.30 A/W). A thin 800 Å In0.52Al0.48As layer was inserted below the electrodes to elevate the electrode Schottky barrier height. A digitally graded superlattice region (660 Å) was also employed to reduce carrier trapping at the In0.53Ga0.47As/In0.52Al0.48As heterointerface which acts to degrade photodiode bandwidth. Bandwidth of opaque electrode MSM's was elevated nearly an order of magnitude over a previous MSM photodiode design with an abrupt heterointerface whereas the bandwidth of transparent electrode MSM's only improved about five times indicating resistive effects may be intervening. Publisher Item Identifier S 0018-9383(97)08292-0.
|Number of pages||6|
|Journal||IEEE Transactions on Electron Devices|
|Publication status||Published - 1997|
|Publication type||A1 Journal article-refereed|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering