HUANG Hua-mao, YOU Yu-ting, WANG Hong etc. Investigation of Low Temperature Hole-injection Layer in GaN-based LED Epitaxial Wafer Grown by MOCVD[J]. Chinese Journal of Luminescence, 2014,35(5): 595-599
HUANG Hua-mao, YOU Yu-ting, WANG Hong etc. Investigation of Low Temperature Hole-injection Layer in GaN-based LED Epitaxial Wafer Grown by MOCVD[J]. Chinese Journal of Luminescence, 2014,35(5): 595-599 DOI: 10.3788/fgxb20143505.0595.
Investigation of Low Temperature Hole-injection Layer in GaN-based LED Epitaxial Wafer Grown by MOCVD
A low-temperature hole-injection layer (LT-HIL) was inserted between multiple-quantum well and electron-blocking layer in GaN-based light-emitting diodes (LEDs) to improve the hole-injection efficiency. The effects of magnesocene (Cp
2
Mg) flow rate and process temperature of LT-HIL in MOCVD epitaxy were investigated. The surface reflectivity and dominant wavelength of epitaxial wafers were measured by photoluminescence spectrometer
the surface profiles were observed by microscope
and the light-output power and forward voltage of fabricated chips were tested by wafer-level auto-measurement system. As the Cp
2
Mg flow rate increases
the crystal quality
flatness
and uniformity of epilayer decrease. Due to the compensation effects in Mg-doped GaN material
the dominant wavelength shows red-shift at first and then blue-shift
the output power of the chip goes up to the maximum then falls down
and the forward voltage goes down to the minimum then rises up. Compared to conventional LED chips without LT-HIL
the output power and forward voltage of the LED chips with Cp
2
Mg moral flow rate of 1.94 mol/min are enhanced by 20.3% and reduced by 0.1 V under the injection current of 20 mA. It is also shown that the gradually changing process temperature can also improve the crystal quality
flatness and uniformity of epilayer
although it is non-principal reason under the condition of large Cp
2
Mg moral flow rate.
关键词
Keywords
references
Wang C K, Chiou Y Z, Sun D J, et al. Low dislocation densities of nitride-based light-emitting diodes with a preflow of NH3 source before growth of AlN buffer layer[J].Jpn. J. Appl. Phys., 2013, 52(1):01AG07-1-5.[2] Chichibu S F, Sota T, Wada K, et al. Impact of internal electric field and localization effect on quantum well excitons in AlGaN/GaN/InGaN light emitting diodes[J].Phys. Stat. Sol.(a), 2001, 183(1):91-98.[3] Lee D Y, Han S H, Lee D J, et al. Effect of an electron blocking layer on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes[J].Appl. Phys. Lett., 2012, 100(4):041119-1-3.[4] Nakamura S, Iwasa N, Senoh M, et al. Hole compensation mechanism of p-type GaN films[J].Jpn. J. Appl. Phys., 1992, 31(5R):1258-1261.[5] Zhang M, Bhattacharya P, Guo W, et al. Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions[J].Appl. Phys. Lett., 2010, 96(13):132103-1-3.[6] Obloh H, Bachem K H, Kaufmann U, et al. Self-compensation in Mg doped p-type GaN grown by MOCVD[J].J. Cryst. Growth, 1998, 195(1):270-273.[7] Han S H, Lee D Y, Lee S J, et al. Effect of electron blocking layer on efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes[J].Appl. Phys. Lett., 2009, 94(23):231123-1-3.[8] David A, Grundmann M J, Kaeding J F, et al. Carrier distribution in (0001) InGaN/GaN multiple quantum well light-emitting diodes[J].Appl. Phys. Lett., 2008, 92(5):053502-1-3.[9] Li H J, Kang J J, Li P P, et al. Enhanced performance of GaN based light-emitting diodes with a low temperature p-GaN hole injection layer[J].Appl. Phys. Lett., 2013, 102(1):011105-1-3.[10] Niu N H, Wang H B, Liu J P, et al. Investigation of p-GaN cap layer of InGaN/GaN MQW blue LEDs grown by MOCVD[J].J. OptoelectronicsLaser (光电子激光), 2006, 17(5):517-521 (in Chinese).