Material and device considerations for selectively doped heterojunction transistors

The material growth, discrete device fabrication, and ring oscillator fabrication for selectively doped heterostructure transistors (SDHT) is described. MBE growth of high mobility GaAs-Al
x
Ga
1-x
AS hetero junction structures has resulted in mobilities as high as
1.5 \times 10^{6}
cm
²
/V sec at ∼4 °K. Devices with g
m
= 309 mS/mm at 77°K and source-drain resistance as low as 0.69 Ω mm have been fabricated. Eleven stage ring oscillators with propagation delays as low as 17.9 psec at 77°K for ∼ 1
\micro
m gate length has been achieved.