Ultrathin InAlN/GaN heterostructures on sapphire for high on/off current ratio high electron mobility transistors

Abstract

We report on InAlN/GaN high electron mobility transistors (HEMTs) grown by metal organic vapor phase epitaxy on sapphire with ultrathin buffers. Two dimensional electron gas (2DEG) exhibiting high mobility (1100 cm2/V s) and low sheet resistivity (356 Ω/□) is achieved at room temperature for a buffer thickness as low as ∼0.1 μm. It is shown that despite a huge dislocation density imposed by this thin buffer, surface roughness is the main factor which affects the transport properties. In addition, sapphire surface nitridation is found to drastically affect the properties of the InAlN/GaN 2DEG. Eventually, HEMTs are processed from these heterostructures. Maximum current densities of 0.35 A/mm and current on-off ratios higher than 109 are measured, which make them suitable for high performance GaN based sensing in harsh environments.

Insights into image contrast from dislocations in ADF-STEM

“…For this study, a thin film of gallium nitride (GaN) with relatively high content (about 10 10 cm 2 ) of edge-and mixed-character dislocations was used (details on GaN growth in [34]). To prepare sample for STEM analysis, a cross-sectional lamella was extracted along the growth direction of the GaN membrane (i.e.…”

Tilt-less 3-D electron imaging and reconstruction of complex curvilinear structures

“…The InAlN/GaN hetrostructure was grown in an AIXTRON 200/4 RF-S metal organic vapour-phase-epitaxy (MOVPE) system on c -plane sapphire substrate. Details on the sample growth can be found elsewhere 62 . For STEM observations a cross-sectional specimen with foil direction was prepared using a conventional focused ion beam (FIB) lift-out technique in a Zeiss NVision40 FIB/SEM workstation.…”

Characterization of InAlN/GaN high-electron-mobility transistors grown on Si substrate using graded layer and strain-layer superlattice

“…5. 17,[24][25][26] From the comparison, it is evident that our InAlN/GaN HEMTs on Si showed excellent BV-R on,sp characteristics without involving the Schottky source/drain 19) or field plate technology. 24,25) In summary, we demonstrated the advantages of growing an In 0.25 Al 0.75 N/GaN HEMT structure using a GL and a thick SLS.…”

“…As the buffer quality was improved, a progressive surface smoothening occurs along with ® H enhancement owing to the reduction in dislocation related to scattering. 2,17) The HEMT devices were fabricated on samples A and B simultaneously to evaluate their electrical characteristics. The device fabrication started with mesa isolation by BCl 3 plasma-based reactive ion etching (RIE).…”