Abstract
The electronic deep level states of defects embedded in freestanding GaN crystals exfoliated from Si substrates by hydride vapour phase epitaxy (HVPE) is investigated for the first time, using deep level transient spectroscopy (DLTS). The electron traps are positioned 0.24 eV (E1) and 1.06 eV (E2) below the conduction band edge, respectively. The capture cross sections of E1 and E2 are evaluated to be 1.65 × 10−17 cm2 and 1.76 × 10−14 cm2 and the corresponding trap densities are 1.07 × 1014 cm−3 and 2.19 × 1015 cm−3, respectively. The DLTS signal and concentration of the electronic deep levels are independent of the filling pulse width, and the depth toward the bottom of the sample, evidenced by the fact that they are correlated to noninteracting point defects. Furthermore, Photoluminescence (PL) measurement shows green luminescence, suggesting that unidentified point defects or complex, which affect the optical characterisitics, exhibit. Despite the Si-based materials, the freestanding GaN exhibits deep level characteristics comparable to those of conventional freestanding GaN, suggesting that it is a desirable material for use in the next generation optoelectronic devices with the large-scalibilityand low production costs.
Highlights
Owing to their unique physical properties, gallium nitride (GaN) and its related compounds are among the most promising materials for optoelectrical devices, such as laser diodes (LDs), ultra violet detectors, light-emitting diodes (LEDs), and high frequency and high power electronics[1,2]
We demonstrated the growth of crack-free FS-GaN 2 inch in diameter and 400 μm in thickness using in situ removal of the Si substrate by hydride vapour phase epitaxy (HVPE) as well as its application in InGaN/GaN blue light emitting diodes (LEDs)[14,15]
We report the origin and electrical properties of electronic deep trap levels incorporated in the HVPE FS-GaN crystals extracted from Si substrates, using deep-level transient spectroscopy (DLTS)
Summary
Owing to their unique physical properties, gallium nitride (GaN) and its related compounds are among the most promising materials for optoelectrical devices, such as laser diodes (LDs), ultra violet detectors, light-emitting diodes (LEDs), and high frequency and high power electronics[1,2]. Because native bulk GaN does not exist, various growth methods, such as ammonothermal, high temperature high pressure (HTHP) growth, Na flux, and hydride vapour phase epitaxy (HVPE) have been employed to obtain FS-GaN to date[3,4,5,6] Among these things, HVPE has good potential because it can provide a high growth rate and relatively high crystallinity[7]. We expect that this study will shed light on the characterization of electronic states embedded in FS-GaN crystals peeled from Si substrates by HVPE, providing impetus to the performance optimization of optoelectronic devices that use FS-GaN crystals based on Si substrates. The optical characteristics of the FS-GaN crystals were measured by photoluminescence (PL) analysis, which was excited using a He–Cd laser of 325 nm wavelength at room temperature
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