Photoelectron emission microscopy observation of inversion domain boundaries of GaN-based lateral polarity heterostructures

Abstract

An intentionally grown GaN film with laterally patterned Ga-and N-face polarities is studied using in situ UV-photoelectron emission microscopy ͑PEEM͒. Before chemical vapor cleaning of the surface, the emission contrast between the Ga-and N-face polarities regions was not significant. However, after cleaning the emission contrast between the different polarity regions was enhanced such that the N-face regions exhibited increased emission over the Ga-face regions. The results indicate that the emission threshold of the N-face region is lower than that of the Ga face. Moreover, bright emission was detected from regions around the inversion domain boundaries of the lateral polarity heterostructure. The PEEM polarity contrast and intense emission from the inversion domain boundary regions are discussed in terms of the built-in lateral field and the surface band bending induced by the polarization bound surface charges.

Polarization-dependent electron affinity of LiNbO3 surfaces

“…Recently, we demonstrated that PEEM is capable of imaging of Ga-and N-face regions of cleaned GaN films. 9 The contrast was due to the enhanced emission from the N-face regions, which was attributed to the photoemission of electrons in the conduction band at the surface induced by band bending. Similarly, a variation in electron affinity and/or band bending could give rise to ferroelectric domain contrast in PEEM.…”

“…13 In contrast, for an actual semiconductor surface, the threshold is dependent on the band structure at the surface, which can vary with the doping and the band bending. 9 It is noted that due to its E g of 3.9 eV, LNO would be considered as a wide band-gap ferroelectric semiconductor. 12 Thus, to understand the origin of the PEEM polarity contrast mechanism of the ferroelectric domains, it is necessary to consider the effects of band bending and electron affinity.…”

Scanning probe investigation of surface charge and surface potential of GaN-based heterostructures

“…1 In prior studies from our group, the surfaces of a GaN-lateral polarity heterostructure ͑LPH͒ have been investigated using PFM, Raman scattering and photoelectron emission microscopy ͑PEEM͒. [4][5][6] In this study, SKPM and EFM have been employed to measure the relative surface potentials and surface charge densities of Ga-and N-face GaN. In order to address the role of adsorbed charge in polarization screening on GaN, the measurements are made before and after a wet chemical treatment that modifies the surface in a controlled way.…”

Characterization of GaN‐based lateral polarity heterostructures

“…365 nm to 13.6 µm for GaN) over both conventional LiNbO 3 and GaAs QPM structures. It is now possible to produce periodically patterned lateral polarity heterostructures (LPH) [1][2][3]. However, the growth of high quality crystalline Ga-and N-face GaN with small inversion domain boundary regions (IDBR) is still a challenge.…”

“…The wurtzite III-nitrides (Al x Ga 1-x N) provide distinct advantages such as a wide window of transparency (e.g. 365 nm to 13.6 µm for GaN) over both conventional LiNbO 3 and GaAs QPM structures. It is now possible to produce periodically patterned lateral polarity heterostructures (LPH) [1][2][3].…”