GaAs-on-Si: Improved MBE Growth Conditions, Properties of Undoped GaAs, High 2DEG Mobility, and Fabrication of High Performance AlGaAs/GaAs SDHT's and Ring Oscillators.

We report improved growth conditions by molecular beam epitaxy (MBE) and fabrication of state-of-the-art AlGaAs/GaAs selectively doped heterostructure transistors (SDHT's) and ring oscillators on Si substrates. In MBE growth, use of minimum As sub 4 Ga flux ratio during initial nucleation combined with in-situ thermal cycles gave a marked improvement in material quality. With this method, FWHM of x-ray rocking curves was measured as low as 135 arc s for a 3.5microns thick GaAs layer on Si. The method also improved the forward and reverse current voltage characteristics of the Schottky diodes making them as good as on GaAs substrates. Although 3microns thick undoped GaAs buffer layers on p-type Si substrates were highly resistive and were fully depleted under a Schottky contact, a parallel n-type conduction path confined in a thin region (