Light-emitting InGaN/GaN Heterojunction Bipolar Transistors *S
Initially, researchers focused on the AlGaN/GaN material system for nitride based heterojunction bipolar transistors (HBTs). However, due to the high ionization energy of Mg acceptors in GaN, the effective hole density in the base layer was limited, severely limiting device performance. However, InGaN alloys have been proven to have lower ionization energy for Mg acceptors, providing a way to increase base carrier density and reduce base plate resistance. At the same time, grading InGaN alloys can optimize the band structure, reduce the conduction band barrier, increase the valence band barrier, thereby increasing current gain and reducing offset voltage. InGaN/GaN heterojunction bipolar transistor based on transparent substrates such as GaN, SiC, sapphire can be used for research in optoelectronics, RF, high-voltage devices, and more. PAM-XIAMEN can customize the growth of InGaN/GaN HBT epitaxial wafers. Please refer to the structure in the following table for details:
1. n-p-n InGaN/GaN Heterojunction Bipolar Transistor Epistructure
| Epi Layer | Material | Thickness | Doping Level |
| Emitter Cap | GaN | – | – |
| Emitter | InGaN | 30nm | – |
| Base | InGaN | – | – |
| Base-Collector Grade | InGaN | – | – |
| Collector | GaN | – | – |
| Sub-Collector | GaN | – | n: 2*1018cm-3 |
| Buffer | GaN | – | – |
| Substrate | Sapphire |
Research has shown that devices prepared with this structure exhibit good performance at high temperatures, indicating that InGaN/GaN HBTs have the potential to be widely used in the field of high-temperature electronics.
2. Research on NpN GaN/InGaN/GaN Heterojunction Bipolar Transistors
Researchers conducted a comparative analysis of NpN GaN/InxGa1 xN/GaN double heterojunction bipolar transistors prepared on Freestanding (FS) GaN substrate and sapphire substrate, revealing the mechanisms by which lattice mismatch and dislocation density affect the performance of III-V nitride HBTs.
The experimental results show that compared with sapphire substrate, FS-GaN substrate has lower dislocation density and better material quality. The improvement in material quality is directly reflected in electrical properties, achieving a maximum collector current density of 12.3kA/cm2 without surface passivation, while obtaining a DC current gain of 90 and a maximum differential gain of 120. The reduction of material defects effectively suppresses the formation of current leakage paths and reduces the density of carrier traps, thereby improving current handling capability.
Further analysis revealed that the diffusion length of minority carriers in FS GaN based HBTs was significantly prolonged, mainly attributed to the decrease in dislocation density and the reduction in the formation of microscopic localized states. In addition, due to its unique low acceptor activation energy and high electron mobility characteristics, at the same doping concentration, InGaN can achieve higher hole concentration, thereby improving p-type doping efficiency. Higher hole concentration can improve the conductivity of p-type InGaN, thereby reducing the resistance of the HBT device and improving performance indicators such as current gain and output power.
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