Use of GaInNAs in the base of heterojunction bipolar transistors (HBTs) on GaAs substrates allows a reduction of the turn-on voltage, V be,on , of the devices, facilitating their use in applications with low power supply voltage (particularly battery operated power amplifiers for mobile communications). Using GaInNAs with N content below 2% and In content of 1-20%, HBTs have been demonstrated with V be,on values lower by 25-400 mV than those of conventional GaAs-based HBTs. The GaInNAs base regions exhibit lower diffusion length than conventional GaAs bases, which reduces current gain and detracts from high-frequency performance, as well as higher base sheet resistance. These adverse effects can be mitigated by proper design tradeoffs of base thickness and nitrogen composition, as well as by compositional grading in the base to provide a built-in quasi-electric field to assist electron transport.
Red light-emitting diodes (LEDs) emitting at 670 nm and employing GaN0.011P0.989 p–n homojunction grown on a (100) GaP substrate by gas-source molecular beam epitaxy with a rf plasma nitrogen source have been obtained. The integrated photoluminescence intensity of GaNP p–n homojunction LED is 5 times stronger than that of Ga0.51In0.49P bulk layer, but the peak width is much broader. Compared to conventional high-brightness AlGaInP red LEDs, our LED structure saves two process steps of etch removing of the GaAs absorbing substrate and wafer bonding to a GaP transparent substrate.
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