Staircase band gap Si1-xGex/Si photodetectors

We fabricated Si1-xGex/Si photodetectors by using a staircase band gap Si1- xGex/Si structure. These devices exhibit a high optical response with a pea k responsive wavelength at 0.96 mu m and a responsivity of 27.8 A/W at -5 V bias. Excellent electrical characteristics evidenced by good diode rectifi cation are also demonstrated. The dark current density is 0.1 pA/mu m(2) at -2 V bias, and the breakdown voltage is -27 V. The high response is explai ned as the result of a staircase band gap by theoretical analysis. (C) 2000 American Institute of Physics. [S0003-6951(00)04528-9].