Defect related dark current and charge injection in Si1-xGex/Si multiple quantum wells

The dark current of five periods Si0.76Ge0.24(60 Angstrom)/Si(300 Angstrom) quantum wells grown at 600, 680, 760 and 850 degrees C were measured at various temperatures and bias voltages. The dark current were determined by the thermalization of carriers at reverse and small forward bias, but controlled by the injection of carriers at large forward bias. Ar -5 V bias, deep levels D1 and D2 or their complex, D1D2 dominate the dark current between 150 and 318 K, while deep levels D3 and D4 or their complex D3D4 play an important role between 77 and 150 K. Strain induced defects can be favorably formed in the Si1-xGex well or Si barrier region depending on the growth condition. At 5 V of bias, the temperature dependence of the dark current shows an exponential behavior which resembles the threshold current of a semiconductor laser, with the characteristic temperature increasing with growth temperature. The bias dependencies of activation energies exhibit a field induced dissociation of D1D2 complex, change of properties of D3D4 complex, and the recombination or thermal activation of injected holes. (C) 1999 Elsevier Science Ltd. All rights reserved.