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9 January 2012 IMEC and Applied Materials researchers say that they have shown for the first time that it is feasible to grow crack-free aluminum gallium nitride (AlGaN) double heterostructures (DH) with thick AlGaN buffer layers on 200mm silicon (Si) substrates using metal organic chemical vapor deposition (MOCVD) [Kai Cheng et al, Appl. Phys. Express, vol5, p011002, 2012]. Such DH structures are aimed at producing field-effect transistors (DHFET) with high breakdown voltage for next-generation power switching devices. In creating DH wafers, the researchers were particularly keen to reduce wafer-bowing effects to less than 50µm, since that is the limit set by equipment designed for mainstream silicon complementary metal-oxide-semiconductor (CMOS) integrated circuit mass production. Double heterostructures of Al Previous work with only a single intermediate layer of Al Sample Al0.5Ga0.5N/Al0.75Ga0.25N thickness (nm) Al0.25Ga0.75N thickness (nm) Wafer bow (µm) Al0.25Ga0.75N (002) Al0.25Ga0.75N (102) A1 200/200 970 67 777 1029 A2 200/200 1260 73 700 934 A3 200/200 1590 59 653 843 A4 200/200 1870 38 645 840 B1 400/400 1900 13 539 1020 B2 600/600 3170 -130.1 499 914 Table 1: Overview of characterization results of Sample Series A and B. The new work introduces a second stress management layer of Al Figure 1: Buffer breakdown voltage versus total layer thickness. The comparison with the paper’s ref. [21] is with previous IMEC/Katholieke Universiteit Leuven work published in 2009. With 200nm-thick intermediate layers (samples A1–4), the material quality indicated by x-ray diffraction rocking curves (sample A4) is comparable with previous results on smaller 4-inch diameter silicon wafers and the best values in the literature. Samples B with thicker intermediate layers were tested with thicker buffer layers, as needed for high breakdown voltage (Figure 1). While sample B2 had the highest breakdown voltage at 1380V, it also has a large concave bowing parameter. Positive bow indicates convex surfaces. The DHFET material was also tested for mobility and carrier concentration of the two-dimensional electron gas (2DEG) of the channel, using van der Pauw Hall measurements. The average electron mobility was ~1766cm Figure 2: DHFET structure. DHFETs (Figure 2) were produced based on buffers grown as for sample B1, which has a breakdown voltage above 950V. After the buffer, a 150nm GaN channel and a 10nm Al The paper concludes: “GaN-based power devices grown on 200mm Si substrates show great potential for integrating GaN processing on a standard silicon technology platform.” The author Mike Cooke is a freelance technology journalist who has worked in the semiconductor and advanced technology sectors since 1997.. The e-commerce company in China offers quality products such as China Through Panel Terminal Blocks , Barrier Terminal Block, and more. For more , please visit Plug In Terminal Block today!
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