New Quantum Photoconductivity and Large Photocurrent Gain by Effective-Mass Filtering in a Forward-Biased Superlattice <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mo>−</mo><mi>n</mi></math></span> Junction

F. Capasso; K. Mohammed; A. Y. Cho; R. Hull; A. L. Hutchinson

doi:10.1103/PhysRevLett.55.1152

New Quantum Photoconductivity and Large Photocurrent Gain by Effective-Mass Filtering in a Forward-Biased Superlattice $p - n$ Junction

F. Capasso, K. Mohammed, A. Y. Cho, R. Hull, and A. L. Hutchinson

Phys. Rev. Lett. 55, 1152 – Published 2 September 1985; Erratum Phys. Rev. Lett. 55, 2229 (1985)

Abstract

We report a new quantum-type photoconductivity in a forward-biased $p^{+} - n$ junction with a superlattice in the $n$ layer. This novel phenomenon is characterized by several striking features: a high photocurrent gain (≃7× $10^{3}$ ), accompanied by a blue shift in the spectral response and a reversal in the direction of the photocurrent, when the forward bias exceeds the built-in potential. Photoconductive gain is caused by the large difference in the tunneling rates of electrons and holes through the superlattice layers, due to their large mass difference (effective-mass filtering). This is the first time that photoconductive gain is observed in a $p - n$ junction.