Radiative lifetime in semiconductors for infrared detection

Abstract

In a previous paper, it was shown that the performance limit of purely radiative IR photon detectors is the background limit, and that the radiative lifetime of van Roosbroeck and Shockley is greatly modified by reabsorption effects. This paper extends the treatment to partially radiatively limited materials in a more general way not restricted to small signal conditions. It is shown that the widespread use of the internal radiative lifetime as a limiting factor in IR detector performance is incorrect by a factor of 25 or more, (the same factor as relates internal and external luminescence efficiencies) and the correct form of the radiative lifetime including reabsorption effects is derived. The detectivity of photoconductive detectors is calculated for a range of internal radiative efficiencies. Large improvements in performance are fundamentally possible if material quality can be improved.