InGaP/GaAs HBT with novel layer structure for emitter ledge fabrication

A novel HBT structure has been utilized to fabricate emitter ledges using a simple, selective wet chemical etch process. This structure eliminates the need for photoresist or dielectric etch masks in the fabrication of self-aligned ledges and enables the use of highly-selective wet chemical etches in forming an InGaP ledge. Small-area devices have been demonstrated with improved gain and excellent high-frequency performance.