Growth kinetics and electronic properties of unintentionally doped semi-insulating GaN on SiC and high-resistivity GaN on sapphire grown by ammonia molecular-beam epitaxy

Abstract

Growth kinetics and electronic properties of unintentionally doped semi-insulating GaN on SiC and high-resistivityGrowth of unintentionally doped ͑UID͒ semi-insulating GaN on SiC and highly resistive GaN on sapphire using the ammonia molecular-beam epitaxy technique is reported. The semi-insulating UID GaN on SiC shows room temperature ͑RT͒ resistivity of 10 11 ⍀ cm and well defined activation energy of 1.0 eV. The balance of compensation of unintentional donors and acceptors is such that the Fermi level is lowered to midgap, and controlled by a 1.0 eV deep level defect, which is thought to be related to the nitrogen antisite N Ga , similar to the "EL2" center ͑arsenic antisite͒ in unintentionally doped semi-insulating GaAs. The highly resistive GaN on sapphire shows RT resistivity in range of 10 6 -10 9 ⍀ cm and activation energy varying from 0.25 to 0.9 eV. In this case, the compensation of shallow donors is incomplete, and the Fermi level is controlled by levels shallower than the 1.0 eV deep centers. The growth mechanisms for the resistive UID GaN materials were investigated by experimental studies of the surface kinetics during growth. The required growth regime involves a moderate growth temperature range of 740-780°C, and a high ammonia flux ͑beam equivalent pressure of 1 ϫ 10 −4 Torr͒, which ensures supersaturated coverage of surface adsorption sites with NH x radicals. Such highly nitrogen rich growth conditions lead to two-dimensional layer by layer growth and reduced oxygen incorporation.

Editors' Choice—On the Radiation Tolerance of AlGaN/GaN HEMTs

“…30 After irradiation, a value of (N d -N a ) = −2.55 × 10 16 cm −3 is needed to yield the correct the sheet carrier density. Because nitrogen vacancies in GaN are known to be shallow donors and Ga vacancies are triple acceptors, 31 it is not surprising that irradiation causes the number of acceptors to significantly increase and (N d -N a ) to decrease.…”

Electrical Characterization of Traps in AlGaN/GaN FAT-HEMT’s on Silicon Substrate by C-V and DLTS Measurements

“…They attribute this defect to dislocation localized in the AlGaN layer. This defect was also studied by Tang [27], with a sample growth of unintentionally doped (UID) semi-insulating GaN on SiC which is mainly employed in GaN HEMT devices. To investigate the defect proprieties and their signatures, they used the PL technique correlated with a typical net TSC electric technique.…”

Defect investigation in Al0.87In0.13N/AlN/GaN heterostructures by scanning force microscopy methods

“…The association of polarization fields, both spontaneous and piezoelectric, with AlInN and GaN allows the induction of polarization charges, which is compensated by formation of a two-dimensional electron gas (2DEG) [3]. For an indium concentration of 17%, AlInN is in lattice-match with GaN, allowing pseudomorphic-growth [12] and the presence of strong polarization fields in AlInN alone itself could cause high 2DEG density (~10 13 cm -2 ).…”

“…They have shown promising results in terms of high emission efficiency, lifetime and have also realized red to UV/blue emission [1]. In the field of electronics, Heterojunction Field Effect Transistors (HFET) like High Electron Mobility Transistors (HEMT) based on AlGaN/GaN or AlInN/GaN have shown promising results in high frequency, high power operatingregime [2,3] as they inherit properties like high electron saturation velocity and high breakdown voltage. However, these devices suffer from short lifetime and poor efficiency because of the presence of defects, poor surface/interfaces and phase-separation at inversion domains produced during their fabrication (growth) [4].…”