Low Pressure Growth of GaAs/AlGaAs Layers on 2N and 3N Substrates in a Multiwafer Reactor

Abstract

The epitaxial growth of GaAs/AIGaAs layers and multilayer structures has been investigated in different low pressure horizontal multiwafer reactors for high throughput capable to handle several 2“ and 3“ wafers in one run. The growth behavior in these reactors will be described with respect to gas flow dynamics. The background carrier concentration is in the 10¹⁴ cm⁻³range. The uptake of dopants (SiH₄) is strongly reduced upon pressure reduction.

The uniformity of GaAs and AIGaAs layer thickness is better than ±3 % over 3“ diameter substrates. The uniformity of composition (measurer on HEMT structures) is better than ± 1 % across 98 % of the wafer areas (± 0.5 % across 75 %). Also the reproducibility is better than 1 %. Results on the uniformity of dopant distribution will also be presented.

HEMT structures grown at low pressure conditions show mobilities of 100,000 cm²/Vs at 77 K and over 210,000 cm²/Vs at 20 K (n_s= 6×10¹¹ cm⁻², spacer thickness 9 nm). HEMT devices with transconductance of 330 mS/mm could be achieved.