Photoconductivity Gain by Si p-n Junction Containing Quantum Dots

摘要

Si junction (of p-i-n diode type) containing Ge of self-assembled quantum dots (SAQD) in a～ 0,6 μm -thick near-surface layer were investigated. Analysis of photo- and electrophysical performances allowed to revel ～ 10-10~3 I_(ph)h(V) photocurrent gain by p-n junction at T=78K upon photodiode radiation with the photon energy corresponding to Si and Ge basic interband transitions. A model is proposed which assumes that SAQDs with a positive charge at T=78K turn out to be trapping centers for electrons/ At "forward" voltages on a photodiode (V>0,2), when the p-layer SAQDs are already partially outside the p-n junction, there takes place electron capture on SAQDs as on adhesion centers under conditions of photocarrier optical generation in Si. In this case, excess concentration of the p-layer electrons forming exsiton-type bound states with quantum dots leads to lowering the p-n junction potential barrier and photocurrent amplification.