Comprehensive Study of Emitter-Ledge Thickness of InGaP/GaAs HBTs

Quantitative analysis of dc characteristics of Ga0.5In0.5P/GaAs heterojunction bipolar devices

“…It may be attributed to the relatively higher space-charge-region width than at higher voltage and is directly proportional to the capture cross section r (¼0.1 Â 10 À15 cm 2 ), bulk trapping density n tb (¼0.5 Â 10 14 /cm 3 ), and trapping density at heterointerface, n ti (¼1.5 Â 10 13 /cm 2 ). [12][13][14] The thermionic diffusion model seems to be inadequate to predict I-V characteristics of a HBT in the complete range of base-emitter voltage. The third base current density component, injection current density from base to emitter J RE , primarily depends on hole diffusion coefficient d p (¼12 cm 2 /s) in quasineutral emitter.…”

“…13 For large area device, the ratio of perimeter to area is small, which reduces the importance of emitter surface recombination current. Thus, I SCR has two components-one from the interface and another from bulk.…”

“…Even the Gummel Plot has been compared only up to applied bias V BE $ 1.3 V where current begins to saturate. As a general observation, Atlas predicts good agreement only below the onset of current saturation and shows sharp discrepancy beyond V BE $ 1.3 V. 12,13 The base sheet resistance is a prime factor for the current gain of HBT and may thus be used for comparing its performance. Moreover, the high current operation beyond applied bias V BE $ 1.2 V in HBT plays an important role in device operation.…”

“…10,11 Using Atlas, many workers have studied HBT DC characteristics, but hardly, these are compared with experimental data at higher range of base to emitter voltage. 12,13 Although, the drift-diffusion model employed by Liou 14 for AlGaAs/GaAs HBT gives the correct trend of collector current characteristics of HBT in the lower base-emitter bias region but does not predict the onset of current saturation at higher bias. 12,13 Although, the drift-diffusion model employed by Liou 14 for AlGaAs/GaAs HBT gives the correct trend of collector current characteristics of HBT in the lower base-emitter bias region but does not predict the onset of current saturation at higher bias.…”

DC and small‐signal comparison of horizontal emitter designs of InGaP/GaAs heterojunction bipolar transistors

“…It was found that the emitter-tobase spacing can be reduced to as little as 0.6 mm without a significant drop in the current gain. A recent study analyzed the optimum emitter-ledge thickness of InGaP/GaAs HBTs required to effectively suppress the surface channel and surface recombination [8].…”