Fabrication of Hemt-on-Si by Movpe for Lsi Applications

We grew selectively doped heterostructures on a Si substrate by metalorganic vapor phase epiaxy (MOVPE) for the first time and fabricated high electron mobility transistors (HEMTs). The conventional selective dry etching process to fabricate enhancement and depletion mode HEMTs on the same wafer, can be used without changing any process conditions. We evaluated the side-gate effect and obtained a critical voltage of 8V. This is large enough for LSI applications. We fabricated HEMTs on two kinds of GaAs-on-Si substrates. One had a small etch pit density (EPD) and poor surface morphology. The other had a large EPD, and better surface morphology. We compared the characteristics of devices on these two substrates, and the degradation of their characteristics was larger for the substrate with a small EPD and poor surface morphology. We conclude that improvement of surface morphology is more important than reduction of dis-location density. For the substrate with better surface morphology, maximum transconductance and K-value, for a gate length of 1 μm were 91% and 84% those of on-GaAs devices.