A comparative study of GaAs- and InP-based HBT growth by means of LP-MOVPE using conventional and non gaseous sources

Abstract

Low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) growth of carbon doped (InGa)P/GaAs and InP/(InGa)As heterojunction bipolar transistors (HBT) is presented using a non-gaseous source (ngs-) process. Liquid precursors TBAs/TBP for the group-V and DitBuSi/CBr 4 for the group-IV dopant sources are compared to the conventional hydrides AsH 3/PH 3 and dopant sources Si 2H 6/CCl 4 while using TMIn/TEGa in both cases. The thermal decomposition of the non gaseous sources fits much better to the need of low temperature growth for the application of carbon doped HBT. The doping behavior using DitBuSi/CBr 4 is studied by van der Pauw Hall measurements and will be compared to the results using Si 2H 6/CCl 4. Detailed high resolution X-ray diffraction (HRXRD) analysis based on 004 and 002 reflection measurements supported by simulations using BEDE RADS simulator enable a non-destructive layer stack characterization. InGaP/GaAs HBT structures designed for rf-applications are grown at a constant growth temperature of T gr=600°C and at a constant V/III-ratio of 10 for all GaAs layers. P-type carbon concentrations up to p = 5·10 19cm −3 and n-type doping concentrations up to n = 7·10 18cm −3 are achieved. The non self-aligned devices (A E = 3·10 μm 2)_show excellent performance, like a dc-current gain of B max = 80, a turn on voltage of V offset = 110 mV (Breakdown Voltage V CEBr,0 > 10 V), and radio frequency properties of f T/f max = 65 GHz/59 GHz. In the non-gaseous source configuration the strong reduction in the differences of V/III-ratios and temperatures during HBT structure growth enable easier LP-MOVPE process control. This is also found for the growth InP/InGaAs HBT where a high dc-current gain and high transit frequency of f T= 120 GHz are achieved.