Improved AlGaN/GaN HEMTs Grown on Si Substrates Using Stacked AlGaN/AlN Interlayer by MOCVD

Abstract

AlGaN/GaN high electron mobility transistors (HEMTs) are grown on 2-inch Si (111) substrates by MOCVD. The stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial growth. The top 1.0 µm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining surface. The XRD results show that GaN(002) FWHM is 480 arcsec and GaN(102) FWHM is 900 arcsec. The AGaN/GaN HEMTs with optimized and nonoptimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are characterized. For the dc characteristics of the device with optimized AlGaN/AlN interlayer, maximum drain current density 𝐼 dss of 737 mA/mm, peak transconductance 𝐺𝑚 of 185 mS/mm, drain leakage current density 𝐼 𝑑𝑠 of 1.7 µA/mm, gate leakage current density 𝐼𝑔𝑠 of 24.8 µA/mm and off-state breakdown voltage 𝑉BR of 67 V are achieved with 𝐿𝑔/𝑊𝑔/𝐿𝑔𝑠/𝐿 𝑔𝑑 = 1/10/1/1 µm. For the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer, current gain cutoff frequency 𝑓𝑇 of 8.3 GHz and power gain cutoff frequency 𝑓max of 19.9 GHz are achieved with 𝐿𝑔/𝑊𝑔/𝐿𝑔𝑠/𝐿 𝑔𝑑 = 1/100/1/1 µm. Furthermore, the best rf performance with 𝑓𝑇 of 14.5 GHz and 𝑓max of 37.3 GHz is achieved with a reduced gate length of 0.7 µm.

L g = 100 nm T-shaped gate AlGaN/GaN HEMTs on Si substrates with non-planar source/drain regrowth of highly-doped n + -GaN layer by MOCVD

“…In addtion, to facilitate device comparison, a standard HEMT was also processed. The detailed process is the same as in our previous work; [12] the spacing of gate-source and gate-drain were both 1.5 µm.…”

Study on AlGaN/GaN growth on carbonized Si substrate

“…12,13) The problem of strain due to the large mismatch in the lattice constant and thermal expansion coefficient can be remedied by introducing AlGaN/AlN buffer layers. [14][15][16][17][18] However, meltback etching of the Si surface due to the reaction between the Si surface and Ga during initial growth is a serious problem. 9,[19][20][21][22] Therefore, an AlN nucleation layer is required to protect the Si surface from Ga. 23) However, there is residual Ga on the sidewall of the flow channel, which is conveyed to the Si substrate surface owing to its reaction with trimethylaluminum (TMA).…”

AlGaN/GaN HEMTs on 4-Inch Silicon Substrates in the Presence of 2.7-μm-Thick Epilayers with the Maximum Off-State Breakdown Voltage of 500 V

“…These benefits make AlGaN/GaN HEMTs on silicon emerge as a promising candidate for power switching applications. [1,2] In terms of high power application, it is important for the AlGaN/GaN HEMT to improve the breakdown voltage (BV). There are several methods to enhance the BV of the AlGaN/GaN HEMT on Si, such as increasing the thickness of buffer layers, improving the quality of the GaN channel layer, and employing the field plate structure.…”