Modeling and Characterization of MTF and Spectral Response at Small Pitch on Mercury Cadmium Telluride

J Berthoz,L Rubaldo,L Martineau,D Leclercq,R Grille,A Kerlain,O Gravrand,N Pere-Laperne,F Chabuel

doi:10.1007/s11664-015-3857-7

Abstract

Space applications are challenging infrared (IR) technologies, demanding the best system performance achievable. This requires covering the entire IR spectrum from short-wavelength infrared (SWIR) to very long-wavelength infrared (VLWIR) for various pixel sizes, which is possible thanks to a well-mastered mercury cadmium telluride technology. Because of its adjustable gap, it can be operated in all the IR bands. Nevertheless, technology optimization requires deep understanding of physical mechanisms. This paper presents computations by finite-element modeling of two aspects of electrooptical performance: spectral response and modulation transfer function (MTF). Computations and characterizations for all IR bands demonstrate the accuracy of our simulations and the state-of-the-art nature of our technology, which performs according to theory. This paper also highlights the capability to measure MTF at very small pitch (10 μm) by a nondestructive method.

Highlights

During the past few years, detector resolution improvement has generated a lot of interest
One of the key performance metrics for detector resolution is the modulation transfer function (MTF), which represents the ability of a system to distinguish contrast for different spatial frequencies
At each Nyquist frequency, the MTF becomes lower with the pitch reduction

Summary

INTRODUCTION

During the past few years, detector resolution improvement has generated a lot of interest. Since pixel pitch reduction improves resolution, the smallest pitch is desired. One of the key performance metrics for detector resolution is the modulation transfer function (MTF), which represents the ability of a system to distinguish contrast for different spatial frequencies. The spectral response is a key figure of merit. Product specifications require precise control of its value at different wavelengths. It is mandatory to be able to simulate the MTF and spectral response. This paper presents computations by finite-element modeling of the spectral response and MTF for the entire infrared band. Computations and characterizations for small-pitch and high-operabilitytemperature (HOT) components are presented for different pitches and cutoff wavelengths

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

CONCLUSIONS