Xiamen Powerway Advanced Material Co.,Ltd., a leading supplier of ultra-high purity crystalline gallium nitride (GaN) and aluminum gallium nitride (AlGaN) materials and other related products and services announced the new availability of 2″/4” size AlGaN–GaN HEMTs Grown on Sapphire Substrates,which is on mass production in 2012. And now PAM-XIAMEN give a example as follows:
2″ GaN HEMT on Sapphire
Nucleation Layer: AlN
Buffer Layer: GaN (1800 nm)
Spacer: AlN (1nm)
Schottky Barrier: AlGaN (21 nm, 20%-30% Al)
Cap: GaN (1.5nm)
2DEG density:>10^13 cm-2 and Mobility>1600cm^2/vs.
RMS roughness(AFM):<0.5NM(5.0um x 5.0um scan area
Sheet resistivity: <200
About GaN hemt on sapphire
AlGaN/GaN high electron mobility transistors (HEMTs) are excellent candidates for high power and high frequency applications at elevated temperatures. Compared with GaAs and InP, GaN has a higher breakdown voltage, high saturated-electron drift velocity and much higher thermal and chemical stability. Also, there exists AlGaN/GaN heterostructure with high conduction band offset and high piezoelectricity resulting in high sheet carrier densities in the 1.0*10^13 cm^-2 range. As a result of these superior material properties and improving material growth and processing technologies, microwave power densities have been demonstrated that are 5–10 times greater than that of corresponding GaAs-based devices. These higher power densities will result in simplifying the design and fabrication of monolithic microwave integrated circuits (MMICs). GaN-based HEMTs are typically grown on either SiC or sapphire substrates. Although, sapphire has less thermal conductivity in comparison with SiC,however it is cheaper and is available in large wafer sizes. GaN HEMTs grown on SiC have demonstrated power density beyond 9 W/mm at X band as compared to 6.4 W/mm for GaN HEMTs grown on sapphire. This difference is due to the higher thermal conductivity of SiC. To date, there have been only few reports of these devices beyond X band. All these results have been on devices fabricated on SiC substrates. Xu et al.have shown that GaN HEMTs grown on sapphire can have competitive performance with thermal management achieved through flip chip bonding of the devices onto a thermally conductive and electrically insulating substrate such as ceramic aluminum nitride.Therefore, GaN HEMTs grown on sapphire substrate can be useful for power application at high frequencies.In this paper, we present record power performance of 0.25 lm gate-length GaN HEMTs on sapphire substrates at 20 GHz. A continuous wave (CW) output power density of 4.65 W/mm was achieved, which represents the highest power density for GaN HEMTs grown on sapphire at 20 GHz.
About GaN hemt on sapphire
AlGaN–GaN HEMTs are promising candidates for highpower, high-frequency, and high-breakdown microwave device applications. However, III-V nitrides grown heteroepitaxially on planar sapphire substrates contain high-density dislocations
in the order of 10^8–10^10 cm^-2 , resulting from the large lattice and thermal expansion mismatch between the III-nitride and the substrate. The high-density dislocations adversely affect the device performance. Dislocation-related device characteristics include leakage current, breakdown voltage, frequency-related noise, and saturated drift velocity of carriers.
Currently, one of the main challenges to enhance RF performance of AlGaN–GaN HEMTs is to reduce the dislocation densities in the bulk and the surface of the AlGaN–GaN heterostructure. Various techniques such as AlGaN–GaN heterostructures over bulk GaN substrates, on AlN/sapphire templates, as well as epitaxial lateral overgrowth (ELO), have been developed for the reduction of GaN dislocation density. However, insulating bulk GaN substrates and AlN/sapphire templates were expensive and not commercially available. Although the ELO technique can effectively improve the crystalline quality of the overgrown layers, there are possible complications of the Si N or SiO patterned-mask on as-grown GaN, which also increases the growth and process time. Additional mask-related drawbacks of ELO include possibilities of impurity contamination and stress-induced tilt in the overgrown layer. GaN grown directly on patterned sapphire substrates is a much simpler means. We have used a maskless and single-step overgrowth technique in reducing the dislocation density and effectively improved the performance of blue LEDs.
About Xiamen Powerway Advanced Material Co., Ltd
Found in 1990,Xiamen Powerway Advanced Material Co., Ltd (PAM-XIAMEN) is a leading manufacturer of compound semiconductor material in China. PAM-XIAMEN develops advanced crystal growth and epitaxy technologies, manufacturing processes, engineered substrates and semiconductor devices. PAM-XIAMEN’s technologies enable higher performance and lower cost manufacturing of semiconductor wafer.In 2001,PAM-XIAMEN has been involved in GaN research.In 2009,PAM-XIAMEN has been mass production for GaN epitaxy on Sapphire and freestanding GaN single crystal wafer substrate which is for UHB-LED and LD. Grown by hydride vapour phase epitaxy (HVPE) technology,PAM-XIAMEN’s GaN wafer has low defect density and less or free macro defect density.Currently PAM-XIAMEN can offer low defect density native (free-standing) GaN in customer-defined orientation including polar (c-plane Ga-face or N-face) and non-polar (a-plane and m-plane), GaN and AlN templates and multi-structure as HEMT structure grown on sapphire and Si or SiC substrates, and ultra-high purity polycrystalline GaN.