High speed pin photodetector with ultra-wide spectral responses

Abstract

We report the design and fabrication of a high speed surface illuminated pin photodetector with a wide spectral response. An InGaAs based detector was grown lattice matched to InP and the device was fabricated using a novel technique to facilitate the direct absorption of incoming photons in the InGaAs layer without being absorbed by any other wider bandgap material. The absorption of a wide spectrum of wavelengths was achieved by recess etching almost all of the InP contact layer above the InGaAs absorption layer of a pin photodiode subsequent to ohmic contacts formation. Theoretical simulation shows responsivities above 0.6 A/W between 900 and 1600 nm and a linear reduction to 0.3 A/W at 650 nm. This makes the detector operational in both visible and near-infrared spectrum. The responsivities are 0.50, 0.77, and 0.67 A/W for 840, 1310 and 1550 nm respectively. These values confirm the potential of the device to be effective in all of the optical fiber communication wavelengths. Our calculations also show that the device can operate above 10 GHz throughout the spectrum.