Large size and low dislocation density bulk gallium nitride (GaN) crystals were successfully grown by original acidic ammonothermal method SCAAT™ (Super Critical Acidic Ammonia Technology). It enabled us to obtain extremely high crystallinity true bulk GaN. In this article, 2-inch size non-polar m-plane GaN and nearly 4-inch size polar c-plane GaN were demonstrated. The dislocation and stacking fault density of m-plane GaN were in the range of 102 to 103 cm-2 and 0 to 5 cm-1, respectively. The full width at half maximum (FWHM) of X-ray rocking curve (XRC) on (10-12) plane was 6.4 arcsec. The dislocation density of c-plane GaN was in the range of 103 to 104 cm-2. The off-angle distribution of nearly 4-inch size c-plane GaN was ±0.006° in the span of 80 mm. The types of dislocations in the c-plane GaN were identified by transmission electron microscope (TEM) observation. Hydride vapor phase epitaxy (HVPE) growth on the SCAA™ c-plane seed was carried out and obtained 2-inch wafer. The crystallinity was comparable to SCAAT™ seed; FWHM of XRC was less than 10 arcsec and off-angle distribution was ±0.017°.
Recent progress of growth techniques of bulk GaN crystals is remarkable for realizing GaN-based power switching devices with a high breakdown voltage. Point defects play important role to characterize the high quality GaN, because structural defects like threading dislocations (TDs) and stacking faults are nearly disappeared. We have been investigating the relation between the near-band-edge (NBE) photoluminescence (PL) lifetime observed at room temperature and the concentration of intrinsic nonradiative recombination centers (NRCs) in n-GaN, of which origins are point defect complexes containing Ga vacancy, by combining positron annihilation spectroscopy (PAS) and time-resolved PL methods [S. F. Chichibu, et al., APL86, 021914 (2005)]. However, PAS becomes less sensitive below the concentration of Ga vacancy ([VGa]) of 10^16 cm^-3. Thus, the development of an alternative way to detect such dilute point defects (<10^16 cm^-3) in high quality GaN crystals is essential.
In this presentation, we will show the quantification of absolute quantum efficiency of radiation (AQE) by employing the omnidirectional PL (ODPL) technique to determine internal quantum efficiency (IQE) of the emission in GaN crystals with different excitation conditions. A high AQE of 8.22% corresponding to IQE of 70.9% was measured at room temperature for the NBE emission of a freestanding-GaN crystal grown by hydride vapor phase epitaxy on a GaN seed crystal manufactured with the acidic ammonothermal method, when cw photo pumping density was 66 W/cm^2.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.