Enhanced bandwidth of traveling-wave photodetector with asymmetric intrinsic region

Abstract

We designed and fabricated traveling-wave photodetector with enhanced bandwidth. Because the saturation velocity of hole is smaller than that of electron, bandwidth limitation in conventional symmetric TWPD results from the difference in electron and hole transit times. For solving this problem, we designed a new structure with asymmetric intrinsic region to equalize the carrier transit times. The intrinsic region on the epitaxial layer consists of InGaAs core and 1.3Q InGaAsP cladding regions. In the whole i-layer thickness with 1 mm, the core region is 0.2 mm thick and the thickness of cladding region is asymmetrically made up. As the thickness of upper cladding region to p-side is decreased, the transit lengths of electron and hole are matched and the bandwidth of TWPD is enhanced. By fabricating TWPD's from three kinds of epitaxial wafers, we prove the enhanced bandwidth of TWPD with asymmetric intrinsic region.