Development of long wave infrared detectors for space astronomy.

摘要

This thesis details the research and development of 10mum cutoff detector arrays conducted at the University of Rochester in conjunction with Rockwell Scientific. Through my data analysis and theoretical modeling of detector characteristics, processes which prevent the detector arrays from meeting low background astronomical specifications are determined and fed back to the manufacturer. The first set of deliveries were manufactured in a banded format with multiple diode structures. Data analysis indicated that the smallest capacitance diode structure exhibited the lowest dark currents and the highest yield of pixels (28%) meeting the goal of less than 100e -/s dark current with adequate (> 45mV) well depth. The mechanisms limiting dark current were found to be surface current at lower biases and tunneling (trap-to-band and band-to-band) at higher biases. In order to reduce stress at the junction during hybridization (a leading cause of the observed tunneling current), a proprietary bonding method was developed by Rockwell Scientific. New detector arrays, manufactured with the optimum diode structure and bonded with the new bonding technique to the HAWAII-1RG multiplexer, showed an impressive 75% of pixels exhibiting dark current less than 30e -/s with sufficient (> 40mV) well depth. Most of these pixels exhibited extremely low dark currents, less than 0.3e -/s. I found that the dark current limiting mechanism at lower biases was still surface current on the front-side, caused by passivation processing techniques. The limiting mechanism at high biases was dislocation-induced early breakdown which took the shape of a screw dislocation (or micropipe) on an I-V curve of dark current, manifesting as a sharp increase in trap-to-band tunneling current. Burst noise was also detected in the source follower unit cell FET of the multiplexer and was fully characterized and explored. It was discovered that the burst noise was a result of oxide trapping of a single charge for most of the observed two-level characteristics. Other, more complicated forms exhibited by some pixels suggested that some multi-carrier traps exist in the bulk silicon close to the channel. With the results presented in this thesis, Rockwell Scientific will again improve their processing and manufacturing techniques on both detectors and multiplexers.