Browsing by Author "Tien Tung Luong"

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Barrier Strain and Carbon Incorporation-Engineered Performance Improvements for AlGaN/GaN High Electron Mobility Transistors
(2015-03-01)
Tien Tung Luong
;
Ho, Yen Teng
;
Binh Tinh Tran
;
Woong, Yuen Yee
;
Chang, Edward Yi
The improvements in electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) grown using metal-organic (MO) CVD by engineering structure, barrier strain, and unintentional carbon incorporation, are demonstrated in this work. Both normal HEMT structure (with a high temperature (HT) AlN buffer) and advanced HEMT structure (with a high-low-high temperature (HLHT) AlN buffer, and a HT AlN interlayer (IL)) present a breakdown voltage higher than 200 V, while a much smaller breakdown voltage of 17V is measured on the conventional structure using a low-temperature GaN buffer. The HT AlN IL inserted in the middle of the conventional HEMT structure introduces a reduction in the tension of the AlGaN barrier, which results in an improvement of the surface morphology (0.46 nm). As a consequence, the two-dimensional electron gas (2DEG) mobility increases by remarkable 46% (1900 cm(2) V-1 s(-1)). The HLHT AlN buffer, substituting for the HT AlN buffer, leads to the enhancement of GaN crystalline quality, which contributes to the performance improvement for HEMTs. The advanced HEMT, using both an AlN IL and an HLHT AlN buffer, produces increases in the DC maximum drain current by 35.5% (similar to 680Amm(-1)), and in the transconductance by 15% (114 mSmm(-1)) in comparison with the normal HEMT with an AlN buffer. The very low leakage current in the advanced HEMTs is caused by optimizing the design of the buffer and modifying growth parameters. Lastly, the reduction of AlGaN barrier tensile strain by inserting the HT AlN IL is promising for an improvement in AlGaN/GaN HEMT reliability.
The Influence of AlN Nucleation Layer on Radio Frequency Transmission Loss of AlN-on-Si Heterostructure
(1970-01-01)
Chang, Shane
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Zhao, Ming
;
Spampinato, Valentina
;
Franquet, Alexis
;
Thi-Hien Do
Reducing radio frequency (RF) transmission loss is a key requirement when fabricating GaN-on-Si RF devices. To get a better insight into the RF loss mechanism in the GaN-on-Si structure, the RF loss of an AlN/Si template is investigated by varying the growth temperature of AlN during a metalorganic chemical vapor deposition process. The results show that the RF loss of the AlN/Si template is dominated by the interface loss due to the p-type conductive channel at the AlN/Si interface, which is induced by the thermal diffusion of Al during the high-temperature growth. Although a low growth temperature of the AlN nucleation layer can suppress the RF loss in the AlN/Si template, it results in a low crystalline quality of AlN for practical use. Optimizing the growth temperature of the AlN nucleation layer is essential to obtain a good balance between the crystalline quality, morphological quality, and RF loss such that the AlN/Si template is suitable for epitaxial growth of the complete GaN-on-Si RF device structure.