Ghosh Saptarsi, Frentrup Martin, Hinz Alexander M, Pomeroy James W, Field Daniel, Wallis David J, Kuball Martin, Oliver Rachel A
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK.
Department of Electronic and Electrical Engineering, Swansea University, Swansea, SA1 8EN, UK.
Adv Mater. 2025 Mar;37(9):e2413127. doi: 10.1002/adma.202413127. Epub 2025 Jan 23.
Thick metamorphic buffers are considered indispensable for III-V semiconductor heteroepitaxy on large lattice and thermal-expansion mismatched silicon substrates. However, III-nitride buffers in conventional GaN-on-Si high electron mobility transistors (HEMT) impose a substantial thermal resistance, deteriorating device efficiency and lifetime by throttling heat extraction. To circumvent this, a systematic methodology for the direct growth of GaN after the AlN nucleation layer on six-inch silicon substrates is demonstrated using metal-organic vapor phase epitaxy (MOVPE). Crucial growth-stress modulation to prevent epilayer cracking is achieved even without buffers, and threading dislocation densities comparable to those in buffered structures are realized. The buffer-less design yields a GaN-to-substrate thermal resistance of (11 ± 4) m K GW, an order of magnitude reduction over conventional GaN-on-Si and one of the lowest on any non-native substrate. As-grown AlGaN/AlN/GaN heterojunctions on this template show a high-quality 2D electron gas (2DEG) whose room-temperature Hall-effect mobility exceeds 2000 cm V s, rivaling the best-reported values. As further validation, the low-temperature magnetoresistance of this 2DEG shows clear Shubnikov-de-Haas oscillations, a quantum lifetime > 0.180 ps, and tell-tale signatures of spin-splitting. These results could establish a new platform for III-nitrides, potentially enhancing the energy efficiency of power transistors and enabling fundamental investigations into electron dynamics in quasi-2D wide-bandgap systems.
对于在大晶格和热膨胀失配的硅衬底上进行III-V族半导体异质外延而言，厚变质缓冲层被认为是不可或缺的。然而，传统的硅基氮化镓高电子迁移率晶体管（HEMT）中的氮化物缓冲层会带来显著的热阻，通过阻碍热提取降低了器件效率和寿命。为了规避这一问题，采用金属有机气相外延（MOVPE）技术展示了一种在六英寸硅衬底上的氮化铝成核层之后直接生长氮化镓的系统方法。即使不使用缓冲层，也能实现关键的生长应力调制以防止外延层开裂，并且实现了与有缓冲结构相当的位错密度。无缓冲层设计使得氮化镓与衬底之间的热阻为（11±4）mK/GW，相较于传统的硅基氮化镓降低了一个数量级，并且是任何非原生衬底上最低的热阻之一。在该模板上生长的氮化铝镓/氮化铝/氮化镓异质结展现出高质量的二维电子气（2DEG），其室温霍尔效应迁移率超过2000 cm²/V·s，可与报道的最佳值相媲美。作为进一步的验证，该二维电子气的低温磁阻显示出清晰的舒布尼科夫-德哈斯振荡、量子寿命>0.180 ps以及自旋分裂的特征信号。这些结果可为氮化物建立一个新平台，有望提高功率晶体管的能量效率，并为准二维宽带隙系统中的电子动力学研究提供基础。
