Ultrafast photodetectors and receiver

Abstract

A family of ultrafast photodetectors and photoreceivers, based on evanescently coupled photodiodes, is described. The waveguide-integrated detectors are monolithically integrated with HEMTs, employing semi-insulating optical waveguides on a semi-insulating InP:Fe substrate. The integration scheme is explained and demonstrated by several examples of broadband and narrowband photodetectors, balanced detectors and photoreceivers, focussing on applications at data rates from 80 to ∼160 Gbit/s.

Technology development towards a generic InP-based photonic-integration foundry

“…Instead of developing one fabrication process that can be used to make a PIC that does a specific optical operation, in a generic foundry approach, the idea is to develop one process that can be used to make PICs that can do as many optical functionalities as possible. Our generic foundry platform is based on the fabrication process of our commerciallyavailable InP-based high-frequency-photodiodes [1] and balanced photodiodes [2]. Both these BBs are made using the same fabrication process.…”

“…This platform will create an opportunity for users to design, develop, and obtain InP-based application-specific PICs (ASPICs) for their particular application. In this work, we have developed a generic foundry platform for receiver-type ASPICs based on our high-end waveguide integrated photodetectors (PDs) with bandwidth up to and beyond 100 GHz [1], and balanced detectors (BPDs) up to 60 GHz [2]. In section 2 of this paper, we will describe the concept of our generic foundry platform.…”

Germanium-based metal-semiconductor-metal photodetectors for 1.550μm optical communication wavelength

“…Ion implantation of silicon [4], hydrogenating amorphous silicon, and SiGe heterojunctions are some of the alternatives to improve silicon absorption for optical communication. 3 SiGe heterojunction detector material is one approach to improve the performance of Silicon.…”

“…The current thus increases with forward bias voltage. When V is negative (reverse bias), the exponential term approaches zero and the current density is -I 0 [3].…”

“…Spectral response of different photodetector material[3] Schematic band diagram of the polycrystalline semiconductor with a periodic array of negatively charged grain boundaries[39] The barrier height as a function of the dopant concentration for polysilicon[40] Grain boundary barrier and parabolic barriers in polysilicon[40] Schematic density of states distribution for an amorphous semiconductor showing the band tails and defect states between the conduction and valence bands Illustration of three main conduction mechanisms in amorphous material Time resolved photoconductance of a-Si:H (a) Linear scale (b) Log-log sale[44] Energy band diagram before contact[41] Energy band diagram after contact[41] Ideal energy band diagrams of (a) Forward (b) Reverse bias[41] Top and cross section view of MSM interdigitated photodiodes (a) Schematic diagram (b) Energy band diagram of MSM structure[53] Potential profile of MSM detector after applying a bias voltage[53] (a) Condition of reach-through voltage (b) Flat band condition (c) V>VFB[53] ..Theoretical I-V characteristics for a Si symmetric MSM with ND= 4x1016 cm-3 and L=12um at 300°k where Case (1): 4>nl = 0.85V and 4>p2 = 0.2v ; Case (2): <J>nl = 0.85V and 4>p2 = lv[53] 35…”