High Power and High External Efficiency m-Plane InGaN Light Emitting Diodes

Abstract

High power and high efficiency nonpolar m-plane (1100) nitride light emitting diodes (LEDs) have been fabricated on low extended defect bulk m-plane GaN substrates. The LEDs were grown by metal organic chemical vapor deposition (MOCVD) using conditions similar to that of c-plane device growth. The output power and external quantum efficiency (EQE) of the packaged 300 ×300 µm2 was 23.7 mW and 38.9%, respectively, at 20 mA. The peak wavelength was 407 nm and <1 nm redshift was observed with change in drive current from 1–20 mA. The EQE shows a minimal drop off at higher currents.

GaN Substrates for III-Nitride Devices

“…However, the use of foreign substrates for the heteroepitaxial growth of GaN in direction different from the [0001] axis favors the generation of stacking faults in addition to high dislocation density, which act as self-formed quantum wells at certain wavelengths and thus prevent emission from intentionally formed QW at shorter wavelengths. LEDs at different wavelengths have been produced during the last several years with different surface orientations, showing no emission shift with increasing current and confirming the absence of polarization induced field in nonpolar QWs for violet [79], [80], blue [81], [82], and green LEDs [83]- [85]. However, the external quantum efficiency in these devices was disappointingly low.…”

“…There are still unresolved questions like In incorporation efficiency in layers grown on GaN substrates with different surface orientations, resulting in different emission wavelength [as in Fig. 6(d) and (e)] in simultaneously grown samples in the [0001], and [11][12][13][14][15][16][17][18][19][20] directions [78], [84], [85] on GaN substrates. Further knowledge gained on this issue as well as a further increase of the substrate size will allow better control of In incorporation for achieving the desired wavelengths.…”

Current Status and Future Prospects of GaN Substrates for Green Devices

“…A few years later, an m-plane LED with higher EQE (EQE 3.1% at 20 mA for 1.79 mW and 435 nm), (16) an m-plane LED with higher output power (EQE 38.9% at 20 mA for 23.7 mW and 407 nm), (17) and a high-brightness semipolar LED (EQE 33.9% at 20 mA for 20.6 mW and 411 nm) (18) were reported. Based on the nonpolar/semipolar device technology, Professor Nakamura founded a venture company called Soraa with two other UCSB professors and they released high-performance LED light bulbs in 2012 (Fig.…”

Implementation of Spatio-Time-Resolved Cathodoluminescence Spectroscopy for Studying Local Carrier Dynamics in a Low Dislocation Density m-Plane In0.05Ga0.95N Epilayer Grown on a Freestanding GaN Substrate

“…Accordingly, there remain concerns if such structural imperfections would cause inhomogeneous incorporation of In during the InGaN growths, [12][13][14] because the In-incorporation efficiency differs depending on the crystallographic orientation of the growth front. As a matter of fact, the full-width at half-maximum (FWHM) values for the near-band-edge (NBE) photoluminescence (PL) peak of the m-plane In x Ga 1Àx N epilayers 5,15) grown by metalorganic vapor phase epitaxy (MOVPE) on FS-GaN were larger than those for c-plane In x Ga 1Àx N epilayers 16) of the same InN mole fractions (x). In order to assess local carrier dynamics in a semiconductor, Merano et al 17) have recently developed a picosecond spatio-time-resolved cathodoluminescence (STRCL) technique to probe InGaAs/AlGaAs pyramidal nanostructures.…”