An extremely low noise heterojunction IMPATT

The avalanche noise characteristics of InP/GaInAs (Ga/sub 0.47/In/sub 0.53/As) and InP/GaInAsP (Ga/sub 0.33/In/sub 0.67/As/sub 0.7/P/sub 0.3/) double drift region (DDR) heterostructure IMPact Avalanche Transit Time (IMPATTs) have been studied. The heterostructure IMPATT's in general are found to be less noisy compared to their homostructure counterparts and in particular the InP/GaInAs DDR is found to generate extremely low noise when the ternary layer width is properly selected. A noise measure of 7.7 dB has been observed at 190 GHz for a GaInAs layer width of 140 nm. Further, a study on the noise contribution from the individual space steps of the depletion layer due to individual noise sources in the generation region has revealed some interesting differences between those of homostructure and heterostructure diodes. Finally, a criterion for low-noise design is also suggested.