High-lifetime GaAs on Si using GeSi buffers and its potential for space photovoltaics

Record-high minority carrier lifetimes exceeding 10 ns are reported for GaA s grown on Si wafers using compositionally graded GeSi buffers coupled with monolayer-scale control of the GaAs/Ge interface nucleation during molecul ar beam epitaxy. The GaAs layers are free of anti-phase domain disorder, wi th threading dislocation densities at or below 2 x 10(6) cm(-2) Secondary i on mass spectroscopy (SIMS) reveals that crossdiffusion of Ga, As and Ge at the GaAs/Ge interface formed on the graded buffers are below detection lim its in the interface region. Test diodes yielded excellent I-V characterist ics, matching those of GaAs diodes on Ge and GaAs wafers, indicating that t o a first order, threading dislocations do not limit device performance. (C ) 2001 Elsevier Science B.V. All rights reserved.