Buffer‐Less Gallium Nitride High Electron Mobility Heterostructures on Silicon

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) m2 K GW−1, 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 cm2 V−1 s−1, 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.