10 W GaInP/GaAs power HBTs for base station applications

Reports on GaInP/GaAs HBTs suitable for high voltage operation as required for base station amplifiers. The high breakdown voltages are achieved by adjusting thickness and doping level of the collector layer. Record BV/sub cbo/ and BV/sub ceo/ values of 80 V and 47 V, respectively, are obtained for a 3.5 /spl mu/m thick collector doped to 4 /spl times/ 10/sup 15/ cm/sup -3/. In order to realize the very high transistor mesa of more than 5 /spl mu/m reliably, the standard HBT process was modified. HBT operation at 2 GHz for high supply voltages up to 32V is demonstrated. Good RF performance is confirmed by f/sub T/ values higher than 20 GHz and usable current densities in excess of 1 /spl times/ 10/sup 4/ A/cm/sup 2/. Power HBTs with an emitter area of up to 5000 /spl mu/m/sup 2/ deliver 10 W of output power at 2 GHz with high efficiencies (PAE=50-79%) and 8-13 dB gain. Compared to LDMOS devices, these power HBTs exhibit a much larger output impedance (e.g., 20 /spl Omega/ for a 4000 /spl mu/m/sup 2/ device), which facilitates combining to very large power amplifiers. Heat-sinking strategies for high power HBTs are discussed based on power results and thermal simulations.