Stress Effect on Current-Induced Degradation of Be-Doped AlGaAs/GaAs Heterojunction Bipolar Transistors

Abstract

The effect of stress on the current-induced degradation of current-voltage characteristics in AlGaAs/GaAs heterojunction bipolar transistors with Be-doped base layers is investigated. Transistors with different orientations of the emitter mesa and different thicknesses of the passivation film are bias tested at room temperature. The results are compared with the stress distributions along the emitter-base junction obtained from a two-dimensional calculation using the boundary element method. It is found that the degradation is caused by the diffusion of Be under high-current density operations and that the flux of Be diffusing from the base layer to the emitter layer is strongly related to the stress distributions around the periphery of the emitter-base junction.

Collector Ideality Factor and Emitter-Base Tunneling Energy at InP/InGaAs Heterojunction Bipolar Transistors

“…. [12] For N E = 7x10 17 cm -3 , Martins and Swart (3) have obtained: n = 1.23, n 0 = 1.02, and, correspondingly, p = 6, in agreement with our results from Fig. 3.…”

“…The technological doping concentrations of the emitter-base junction, determined by SIMS, are: N E = 7x10 16 cm -3 and N B = 2x10 18 cm -3 . This stress induced by silicon nitride layer under the emitter mesa sidewall produces a piezoelectric-like effect (12)(13)(14)(15). This changes drastically the effective concentrations from this region (15), which become: N E = 1.7x10 18 cm -3 and N B = 5x10 18 cm -3 .…”

“…3. The relation [12] is valid for emitter concentrations in the range N E ≤ 5x10 17 cm -3 . This is the principal domain of the emitter technological concentration values for InP/InGaAs heterojunction bipolar transistors.…”

Comparison of H+ and He+ implant isolation of GaAs-based heterojunction bipolar transistors

“…[1][2][3][4][5][6] This mechanism is absent in C-doped base HBTs, 7 but even in these devices one can observe gain degradation in some cases when collector current densities approach 10 5 A cm Ϫ2 . For devices with high base doping levels ͑Ͼ4ϫ10 19 cm Ϫ3 ͒ of Be, Zn, or Mg, the current gain may decrease during operation due to recombination enhanced diffusion of charged interstitial dopants into the adjoining emitter layer.…”