Substrate Impurity Incorporation Mitigation for Improved AlGaN/GaN-ON-Si RF Performance




Saha, Rony

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A conductive interface is formed between Silicon substrate and AlN nucleation layer during high-temperature deposition. This parasitic conduction path is highly detrimental as it is capacitively coupled to the GaN HEMT 2DEG channel. Moreover, the presence of significant lattice mismatch and thermal mismatch between the AlN nucleation layer and Si leads to a very large threading dislocation density (TDD) within the AlN layer thereby creating a leakage path, significant electron scattering, and charge carrier trap centers. The parasitic conduction path dissipates the radio-frequency (RF) signal, which increases with operation frequency, in transistors manufactured on such a lossy Si substrate and large TDD AlN nucleation layer. As a result, they fail to deliver good RF amplifier performance at high frequency in terms of gain, power, and efficiency. This undesirable conductive path is suppressed after developing and optimizing a robust novel interface technology, and the AlN nucleation layer materials are significantly improved. As a result, the RF signal loss on AlGaN/GaN on Silicon materials is reduced substantially, well below 0.4 dB/mm for frequencies up to 50 GHz, compared to conventional AlGaN/GaN on Silicon heterostructures. For AlGaN/GaN HEMTs, this improvement of the RF performance is critical for high-power/high-frequency operation with enhancements to RF switching speed, power, gain, and efficiency.



RF loss GaN HEMT, AlN


Saha, R. (2021). Substrate impurity incorporation mitigation for improved AlGaN/GaN-ON-Si RF performance (Unpublished dissertation). Texas State University, San Marcos, Texas.


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