“…More recently, a group consisting of Messrs. Perlman, Oldham, Williams, Feucht, and Milnes h a v e carried out a m o r e intensive investigation into the Ge-GaAs system originally studied by Anderson and extended the w o r k to other systems as G e -S i and In_P-GaAs. In a series of papers (15)(16)(17)(18)(19)34), the general conclusion reached seems to be that there are a large n u m b e r of unexplained discrepancies which m a k e uncertain the complete validity of the discontinuous e n e r g y -g a p model. Continuing w o r k by H o ward and Fang (20, 21) on n -n G e -G a A s diodes has shown that these heterojunctions have subnanosecond switching times but suffer the disadvantage of having a low reverse b r e a k d o w n voltage.…”