An extremely low offset voltage AlInAs/GaInAs heterostructure-emitter bipolar transistor

A new Al_0.48In_0.52As/ Ga_0.47In_0.53As heterostructure-emitter bipolar transistor (HEBT) with a very low offset voltage of 40 mV has been fabricated by molecular beam epitaxy. From the theoretical analysis and experimental results, it is found that a 500-Å thick emitter used in the studied device can effectively eliminate the potential spike at the N–AlInAs/n–GaInAs heterointerface. However, a degenerate current gain of about 25 is obtained, attributed to the increase of recombination current at the neutral-emitter regime. This is caused by the short hole diffusion length of GaInAs, which reduces the emitter injection efficiency. Due to the small surface recombination velocity, the emitter edge-thinning design is not essential to improve the device performance of our proposed AlInAs/GaInAs HEBT.