Performance Characteristic of Two Color Midwave HgCdTe Detectors Above 80K.

摘要

Two color mid-wave triple layer heterojunction HgCdTe detectors were studied using temperature-dependent current-voltage (I-V) measurements, temperature-dependent spectral response measurements, and temperature-dependent noise measurements. The reverse biased dark current shows diffusion-limited behavior for T > 125 K. The same data shows evidence for generation- recombination type behavior at temperatures between 100K and 125K. For temperatures less than 100K, the measurements are limited background by photon flux, even though these measurements are performed at nominal zero background. The upper junction shows reverse breakdown voltages on the order of about 400mV, while the bottom junction shows no breakdown for V < 500 mV. At 80K, the RoA product is in excess of 1 x 10(exp 6) Ohms sq cm. In forward bias, the current- voltage characteristics of the lower junction are diffusion limited for all temperatures, while at lower temperatures, the upper junction showed generation- recombination behavior. Optical measurements found a cutoff wavelength of about 4 micrometers the lower junction and about 4.5 micrometers for the upper junction. The temperature dependence of the cutoff wavelength agrees with theory. The spectral crosstalk was less than 5%. At 80K, the noise of the shorter wavelength junction could not be distinguished from the instrument noise, regardless of bias. For the longer wavelength junction, the noise at lower frequencies increases with bias. There is no difference in the noise characteristics when either the photon flux or the temperature is increased.