Low-temperature and ammonia-free epitaxy of GaN/AlGaN/GaN heterostructure

Abstract

Wide band gap semiconductors are very attractive because of their broad applications as electronics and optoelectronics materials − GaN-based materials being by far the most promising. For the production of such nitride-based optical and power devices, metal-organic chemical vapour deposition (MOCVD) is routinely used. However, this has disadvantages, such as the large consumption of ammonia gas, and the need for high growth temperature. To go beyond such a limit, in this study we successfully developed a remote plasma assisted MOCVD (RPA-MOCVD) approach for the epitaxial growth of high-quality GaN/AlGaN heterostructures on 4H-SiC substrates. Our RPA-MOCVD has the advantages of lower growth temperature (750 °C) compared to conventional MOCVD route, and the use of a remote N2/H2 plasma instead of ammonia for nitrides growth, generating in situ the NHx (x = 0−3) species needed for the growth. As assessed by structural, morphological, optical and electrical characterisation, the proposed strategy provides an overall cost-effective and green approach for high-quality GaN/AlGaN heteroepitaxy, suitable for high electron mobility transistors (HEMT) technology.

Exciton Effects in Low-Barrier GaN/AlGaN Quantum Wells

“…The high energy peak consists of four (or five) components (xi band, continuous lines in Figure 4) related to the QWs structure, and it is followed by the series of LO phonon replicas (dotted lines). In nitride based heterostructures, the main emission bands xi are tipically related to exciton complexes (free, localised, or bound excitons, etc) and/or free-carriers [20]. The phonon replicas refer to x4 band (dark blue line) and are interspaced by about 92 meV, which corresponds to the bulk GaN LO phonon energy [21].…”

“…and free-carrier recombination are typically observed. 26,27 Therefore, further investigation is needed for a clear attribution. In Table S2 are reported the energy values of x i transitions for all of the samples.…”