Abstract
The formation and diffusion of point defects have a detrimental impact on the functionality of devices in which a high quality AlN/GaN heterointerface is required. The present paper demonstrated the heights of the migration energy barriers of native point defects throughout the AlN/GaN heterointerface, as well as the corresponding profiles of energy bands calculated by means of density functional theory. Both neutral and charged nitrogen, gallium, and aluminium vacancies were studied, as well as their complexes with a substitutional III-group element. Three diffusion mechanisms, that is, the vacancy mediated, direct interstitial, and indirect ones, in bulk AlN and GaN crystals, as well at the AlN/GaN heterointerface, were taken into account. We showed that metal vacancies migrated across the AlN/GaN interface, overcoming a lower potential barrier than that of the nitrogen vacancy. Additionally, we demonstrated the effect of the inversion of the electric field in the presence of charged point defects and at the AlN/GaN heterointerface, not reported so far. Our findings contributed to the issues of structure design, quality control, and improvement of the interfacial abruptness of the AlN/GaN heterostructures.
Highlights
III–V nitride materials, in particular GaN and AlN, found many interesting applications in high-power, high-temperature electronic and optoelectronic devices, such as laser diodes (LDs), light emitting diodes (LEDs), near-ultraviolet distributed Bragg reflectors (DBRs), transparent biosensors, or plasma-wave terahertz emitters [1,2,3,4,5]
Due to a wide direct band gap lying in the range from 3.47 eV (GaN) to 6.09 eV (AlN) [6,7,8], the AlxGa1−xN alloy system enabled the fabrication of photodetectors and high electron mobility transistors (HEMTs) [9,10,11]
The aim of the present paper is to find the heights of the migration energy barriers of all native point defects throughout the AlN/GaN interface, which were exempt from the analysis of papers [15,16]
Summary
III–V nitride materials, in particular GaN and AlN, found many interesting applications in high-power, high-temperature electronic and optoelectronic devices, such as laser diodes (LDs), light emitting diodes (LEDs), near-ultraviolet distributed Bragg reflectors (DBRs), transparent biosensors, or plasma-wave terahertz emitters [1,2,3,4,5]. The main component of the active layers in such device structures are the AlGaN/GaN heterostructures whose interfacial quality is crucial for achieving a high performance of the AlGaN-based devices. The AlN/GaN interfacial quality can be degraded by a number of factors including a high density of threading dislocations, stacking faults, interface roughness, point defects, or cracking highly strained AlN layer. AlGaN/GaN HEMTs can operate in a harsh environment where a high-energy particle radiation can be present. Under such harsh conditions the reliability, performance and life-time of the device can be influenced by the presence of defects in the structure and their diffusion
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