P-type doping of GaN by magnesium ion implantation

Abstract

Magnesium ion implantation has been performed on a GaN substrate, whose surface has a high thermal stability, thus allowing postimplantation annealing without the use of a protective layer. The current–voltage characteristics of p–n diodes fabricated on GaN showed distinct rectification at a turn-on voltage of about 3 V, although the leakage current varied widely among the diodes. Coimplantation with magnesium and hydrogen ions effectively suppressed the leakage currents and device-to-device variations. In addition, an electroluminescence band was observed at wavelengths shorter than 450 nm for these diodes. These results provide strong evidence that implanted magnesium ions create acceptors in GaN .

Cathodoluminescence Study on Thermal Recovery Process of Mg‐Ion Implanted N‐Polar GaN

“…The Mg‐ and H‐ions implanted diode with superior rectification at a forward on‐voltage of about 3 V was characterized by CL analysis at low temperature and compared to the epitaxial sample. The implanted sample was prepared by implanting with both Mg‐ and H‐ions into N‐polar n‐type GaN(000) substrate through a 30 nm‐thick SiN film, where the maximum concentration of Mg‐ and H‐ions were 1.4 × 10 19 and 2.1 × 10 20 cm −3 at the near surface, respectively . This implantation condition produced the shallow junction depth of 0.1 µm under the assumption of full activation of Mg acceptors .…”

“…Feigelson et al exhibited p‐type conductivity for the sample with Mg‐ion implantation into GaN and subsequent multicycle rapid thermal annealing with the AlN protective overlayer . Narita et al recently demonstrated the superior rectification of p–n diodes implanted with both Mg and hydrogen (H)‐ions into N‐polar GaN(000) surface which is thermally more stable than Ga‐polar surface, allowing post‐implantation annealing without the protective overlayer . Coimplantation with H ions was expected to reduce the apparent formation energy of Mg‐substituted Ga sites by producing intermediate Mg‐H complexes .…”

“…Coimplantation with H ions was expected to reduce the apparent formation energy of Mg‐substituted Ga sites by producing intermediate Mg‐H complexes . Narita et al also indicated the presence of high‐density point defects in the corresponding diodes . Uedono et al indicated that post‐implantation annealing not only recovers implantation‐induced damage but also probably generates nitrogen vacancy (V N ) complexes .…”

Strain Recovery and Defect Characterization in Mg‐Implanted Homoepitaxial GaN on High‐Quality GaN Substrates

“…Currently, there is a lack of a mature doping process to form selective p‐type regions in GaN. Ion implantation is assessed as an increasingly relevant processing technique for wide bandgap semiconductor materials, particularly as a means to achieve p‐type doping in GaN . Postimplantation annealing is required to relieve the lattice displacements caused by the implantation process and activate dopants.…”

Detection of deep-level defects and reduced carrier concentration in Mg-ion-implanted GaN before high-temperature annealing

“…Very recently, the successful formation of p-type regions on GaN epitaxial layers on free-standing GaN substrates by Mg ion implantation has been confirmed by observing the rectifying characteristics of p-n junctions formed by applying multicycle rapid thermal annealing, 5,6 standard high-temperature annealing, 7,8 and coimplantation of the N-face of GaN with Mg and H ions. 9 However, it has been reported that defects remain in the Mg-implanted GaN layer even after high-temperature annealing on the basis of positron annihilation spectroscopy (PAS) and photoluminescence (PL) studies. 10,11 To control the electrical properties of Mg-implanted GaN, an electrical measurement should be carried out to understand the thermal behavior of the defects by starting from a sample before high-temperature annealing for the activation of Mg acceptors.…”