Low Turn-on Voltage InGaP / GaAsSb / GaAs DHBT Grown by MOCVD
In this work, an InGaP/GaAsSb/GaAs DHBT with carbon doping up to 4E19/cm GaAsSb base was studied. A current gain of 115 at the collector current density of 25KA/cm2 was achieved for the Rbs of about 530ohm/sq. Over 100mV turn-on voltage and knee voltage reduction and 2/3 offset voltage were obtained for the GaAsSb based HBT compared with the standard InGaP/GaAs SHBT. The DC gain of the device is less temperature dependence (the DC gain variation is less than 3% for the temperature range from 25 degree C to 100 degree C.) due to the larger valence band discontinuity between InGaP emitter and GaAsSb base, compare with the standard InGaP/GaAs SHBT. These results indicate that GaAsSb is a great choice for the base material of a low turn-on voltage HBT.
Pathway for HBT Turn-on Voltage Reduction on a GaAs Platform
The fundamental lower limit on the turn-on voltage of GaAs-based bipolar transistors is reduced with the use of a low energy-gap base material, GaInAsN. A 115 mV reduction in the turn-on voltage over a wide range of base sheet resistance values (250 to 850 Ω/) is established relative to both GaAs BJTs and conventional InGaP/GaAs HBTs with optimized base-emitter interfaces. InGaP/GaInAsN DHBTs structures with high p-type doping levels (~ 3x10 19 cm -3 ) and acceptable DC and RF characteristics (βmax ~ 75, ft ~ 64 GHz) are demonstrated. The reduction in turn-on Vbe enabled by lattice-matched GaInAsN base layers should permit improved management of the voltage budget, and enhance the overall performance, of both wired and wireless GaAsbased RF circuits.
GaAs-GaAsSb based heterojunction bipolar transistor
The fabrication of the first GaAs-GaAsSb based heterojunction bipolar transistor is reported. Maximum current gains of 25 at a base current of 1 mA have been measured on devices employing a p-type 1000 AA GaAs/sub 0.93/Sb/sub 0.07/ base doped at 1*10/sup 19/ cm/sup -3/ and GaAs emitter and collector regions with graded heterointerfaces. At present, devices so fabricated show unstable behaviour.