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Effects of substrate tilting in substantial improvement of DC performance of AlGaAs/GaAs n-p-n DHBTs grown by MBE

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3 Author(s)
Chand, N. ; AT&T Bell Lab., Murray Hill, NJ ; Berger, P.R. ; Dutta, N.K.

A marked improvement has been observed in the DC performance of Al 0.5Ga0.5As/GaAs/Al0.5Ga0.5As double-heterojunction bipolar transistors (DHBTs) by tilting the (100) GaAs substrates 3° towards <111>A. On the tilted substrate, the surface, space charge, and bulk recombination currents are reduced, and the quality of AlGaAs/GaAs heterointerfaces is improved. As a result, both the emitter injection efficiency (η) and base transport factor are increased, leading to a substantial increase in current gain with a marked reduction of its current and junction geometry dependence. The device characteristics and current gain changed very little between 25 and 100°C on both substrates. The improved bulk and interfacial quality of AlGaAs/GaAs heterostructures on the misoriented substrates is confirmed by TEM cross sections and SIMS measurements and is due largely to the lower affinity of Ga-like surface steps for defects and impurity incorporation

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Electron Devices, IEEE Transactions on  (Volume:38 ,  Issue: 12 )