Proceedings Article | 14 May 2007
Proc. SPIE. 6542, Infrared Technology and Applications XXXIII
KEYWORDS: Signal to noise ratio, Photon counting, Avalanche photodetectors, Mercury cadmium telluride, Sensors, Diffusion, Interference (communication), Diodes, Medium wave, Absorption
In this communication we report high performance gain characteristics measured at T=77K in electron injected MW
HgCdTe APDs. A full set of characterisations, including gain, excess noise, dark current and first measurement of the
impulse response, was performed on test arrays of backside illuminated pin type MW APDs, manufactured at CEA LETI
using an MBE grown HgCdTe absorption layer. A record high avalanche gain of M=5300 have been demonstrated in
these diodes, associated with a low noise factor, F=1.0-1.3, and low dark current. The sensistivity of the APD is
discussed in terms of the impact of the distribution of the gain in the structure for different applications and we have
estimated a shot noise equivalent input current, Ieq_in=2.0 10<sup>-13</sup> to 1.0 10<sup>-12</sup>A, for continuous measurements, and a dark
count rate for photon counting applications DCR=2.7 10<sup>6</sup> s<sup>-1</sup>. The first measurements of the impulse response of the MW HgCdTe APDs showed that the band width was only weakly
dependent on the gain, in coherence with the dominant electron multiplication evidenced by the low value of the noise
factor. At the maximum gain, M=5000, we measured a risetime of t<sub>10-90</sub>=88ps and a fall time of t<sub>90-10</sub>=2.4ns, yielding a record high band width product of GBW=723GHz (BW=145MHz), mainly limited by the diffusion and life time of the
minority electrons.
