CMOS Integrated 32 A/W and 1.6 GHz Avalanche Photodiode Based on Electric Field-Line Crowding

Abstract

This paper presents a new Si CMOS linear-mode avalanche photodiode (APD) based on an electric field distribution formed by field-line crowding. In this structure, a spherical avalanching electric field is enforced by field-line crowding due to the curvature of the half-sphere cathode (n-well). The electric field extends radially and, therefore, the entire lowdoped epitaxial layer serves as charge collection zone. This APD can provide high responsivity and bandwidth due to its thick absorption zone and drift-based carrier transport. Measurements using a 675 nm laser source at 200 nW optical power show a maximum bandwidth of 1.6 GHz while the responsivity is 32 A/W. In addition, a maximum responsivity of 3.05×103 A/W at 5 nW optical power is achieved. Due to the high avalanche gain, large bandwidth, and CMOS compatibility without any process modification, this APD is a promising optical detector for many applications.