Enhancement of quantum efficiency in thin photodiodes through absorptive resonance

Abstract

The spectral response of resonantly enhanced photodiodes is analyzed theoretically and verified experimentally. Comprehensive design guidelines and formulas are given for device structures containing a metal reflector, a contact layer, an optional grading layer, an absorbing layer, and a quarter-wave stack (QWS). The analysis shows, for instance, that the quantum efficiency of a Schottky photodiode with a 162-nm GaInAs absorbing layer can be enhanced 3.7 fold by using a 41-layer AIInAs/AlGaInAs QWS. The number of layers required could be much lower for other material systems and/or if the substrate is removed. Experimentally, 50% enhancement is demonstrated for a 475-nm thick absorbing layer at 1.52 pm by using a 16-layer QWS. The resonance width is -4.4%. This type of structures should be very valuable for very small size ultrafast photodiodes and for optoelectronic integration.

Fabrication of high-speed resonant cavity enhanced Schottky photodiodes

“…High-speed RCE photodetector research has mainly concentrated on using p-i-n type photodiodes, where near 100% quantum efficiencies along with a 3-dB bandwidth of 17 GHz have been reported [9]. There are only a few reports on RCE Schottky photodiodes, where a 2-fold enhancement has been observed for RCE InGaAs-InAlAs based Schottky photodiodes [10]. In this letter, we report our work on design, fabrication and testing of high-speed RCE Schottky photodiodes for operation at 900 nm.…”

Tunable Omnidirectional Resonance in Metal-Insulator-Metal Structures

“…The interface between two materials with dielectric constants with opposite signs can support localized electromagnetic waves called surface plasmon polaritons (SPPs). Structures based on SPPs have received much attention for their ability to confine light to metal-dielectric surfaces, which allows for optical mode dimensions below the diffraction limit [1]- [3]. Subwavelength-confined propagating SPPs in nanostructured films are emerging as an information carrier for highly integrated devices [4], [5].…”

An intra-chip free-space optical interconnect

“…A VCSEL's optical output can be directly modulated by its current, and the modulation speed can reach tens of Gbps [14,15]. The photodetectors can be either integrated on the CMOS chip as silicon p-i-n photodiodes [16], or fabricated on the same GaAs chip with the VCSELs as resonant cavity photodiodes [17,18]. In the latter case, an InGaAs active region is enhanced by the resonant cavity similar to a VCSEL, and the devices offer a larger bandwidth and is well suited for this FSOI system.…”