Together with the Nanyang Technological University in Singapore AIXaTECH demonstrated metal-insulator-semiconductor high-electron-mobility transistors (MISHEMT) with a low-temperature epitaxy (LTE)-grown single crystalline AlN gate dielectric. The excellent results achieved make LTE grown AlN an excellent alternate material as gate dielectric for GaN-based MISHEMT application and put AIXaTECH on the cover of the publication.
Dr. Dikme, CTO of AIXaTECH, explains: “Prior to the overgrowth of the HEMT, the growth of LTE AlN on GaN on sapphire was investigated. This basic work was necessary since LTE AlN only on GaN on sapphire can be clearly identified by XRD whereas the GaN layers on silicon have AlN interlayers falsifying the XRD results. Several processes have been made with different starting conditions. The samples have been investigated by HR-XRD, AFM, SEM and cross-section TEM. With the right starting conditions the LTE AlN on GaN creates a sharp interface with a crystalline crossover from MOCVD GaN to LTE AlN.”
The Nanyang team under the lead of Professor Ng Geok Ing summarized the results: ”The 400°C annealed MISHEMT exhibited an increase of 15% in gmmax, an order of magnitude reduction in reverse gate leakage and about a 3% suppression of drain current (ID) collapse. The increase of gmmax by post-gate annealing is consistent with the increase of 2DEG mobility.” And Dr. Dikme adds: “I’m really happy that the colleagues in Singapore achieved these excellent results and like to thank for the excellent co-operation. Of the same importance as the excellent HEMT features is however that the crystallinity of the LTE grown layers is even higher or even not possible with standard procedures as metal-organic chemical vapor deposition (MOCVD) and plasma-enhanced atomic layer deposition (PEALD).”