Latest Developments of HgCdTe e-APDs at CEA LETI-Minatec
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- Rothman, J., Perrais, G., Ballet, P. et al. Journal of Elec Materi (2008) 37: 1303. doi:10.1007/s11664-008-0449-9
In this communication, we report on the electro-optical characterization of planar back-side-illuminated HgCdTe electron initiated avalanche photodiode (e-APD) test arrays with cut-off wavelengths λc = 2.4 μm, λc = 4.8 μm, and λc = 9.2 μm. The e-APDs were manufactured at LETI using absorption layers grown by molecular beam epitaxy (MBE). We present measurements of the distributions in gain, noise, and equivalent input dark current. The mid-wave (MW) diodes yielded a very low dispersion (2%) and high operability (98%) for gains up to M = 200. The excess noise factor and equivalent input current (Ieq_in) operability were slightly lower, due to defects in the depletion region. The lowest measured value of Ieq_in = 1 fA corresponds to the lowest level measured so far in HgCdTe e-APDs and opens the way to new applications. The gain in the long-wave (LW) diodes was limited by tunnelling currents to a value of M = 2.4, associated with an average noise factor F = 1.2. A gain of M = 20 at a bias of −22.5 V was demonstrated in the short-wave (SW) e-APDs.