The mechanism of the photoresponse blueshifts for the n-type conversion region of n+-on-p Hg0.722Cd0.278Te infrared photodiode

The photoresponse blueshift of the n-type conversion region for n+-on-p Hg0.722Cd0.278Te infrared photodiode is numerically investigated by considering the conduction band nonparabolic characteristic and band gap narrowing effect. It has been shown that the photoresponse position of the n-type conversion region shifts remarkably toward high energy. The shift energy is 37 meV higher than that of the p region. The result can be used to explain quantitatively the recent experimental observation of the blueshift of the photoluminescence peak for the n-type conversion region. The following three contributions are considered: (i) the Burstein–Moss shift considering a nonparabolic conduction band, (ii) the band gap narrowing effect, and (iii) the Hg-vacancy-induced acceptor trap level. It is concluded that the band gap narrowing and nonparabolic effects play an important role in the photoresponse of n+-on-p HgCdTe infrared photodiode with heavy doping concentration.