TEM characterization of III-V diode structure grown on GeOI structures

Abstract

A highly sensitive semiconductor device, avalanche photo diode, exploits photoelectric effect to convert light to electricity. APDs which can act like photo detectors provide a built-in first stage gain through avalanche multiplication. When the photo generated carriers acquire enough energy from the electric field to impact ionize, internal current gain can be achieved in avalanche photodiodes. [1]Therefore, by using APD instead of a pin diode or converting the weak optical signal into an electrical current, the internal gain mechanism can improve the signal-to-noise ratio (SNR) of an optical receiver. However, the avalanche process is stochastic in nature and increased sensitivity is limited by the level of excess noise generated by avalanche process. This

report will provide detail of Excess Noise Measurement and it’s setup for APD current. It will mainly focus on how the set up is done and detail explanation of noise measurement set up circuit.

Part of this project will include the step by step preparation of TEM sample. The quality of grown III-V diode structure which grown on Ge on insulator on Si(GeOI) substrates by MOCVD technique is needed to determine the feasibility of monolithic

integration of III-V and Si. Transmission electron microscopy (TEM) is a powerful technique to examine the quality of a sample down to atomic scale. III-IV diode structures grown on GeOI under various growth conditions will be prepared into ultra

thing layer for cross section view and planar view and samples will be examined by high resolution TEM. The investigation will focus at the III-V and Ge interface, where most of the possible defects originated.