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  物理学   3篇
  2014年   3篇
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The high power GaN-based blue light emitting diode(LED) on an 80-μm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition(MOCVD), hydride vapor-phase epitaxial(HVPE), and laser lift-off(LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction(XRD), high resolution transmission electron microscope(HRTEM), Rutherford back-scattering(RBS), photoluminescence, current-voltage and light output-current measurements. The width of(0002) reflection in XRD rocking curve, which reaches 173 for the thick GaN template LED, is less than that for the conventional one, which reaches 258. The HRTEM images show that the multiple quantum wells(MQWs) in 80-μmthick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-μm-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80-μm-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation.  相似文献
2.
The high power GaN-based blue light emitting diode (LED) on an 80%tm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epi- taxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173" for the thick GaN template LED, is less than that for the conventional one, which reaches 258". The HRTEM images show that the multiple quantum wells (MQWs) in 80%tm- thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-~m-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80%tin-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation.  相似文献
3.
GaMnN/GaN multilayers and conventional GaMnN single layers are grown by metal-organic chemical vapor deposition. Both kinds of samples show room-temperature ferromagnetism. After thermal annealing, the sample with GaMnN/GaN multilayer structure displays a larger coercivity and better thermal stability compared to the GaMnN single layer. The annealing effects on Vca related defects are observed from photoluminescenee measurements. Moreover, a different magnetic behavior is also found in the annealed GaMnN films grown on different (n-type GaN and p-type GaN) templates. These kinds of structure-dependent magnetic behaviors indicate that defects or carriers transformation introduced during annealing may have important effects on the electronic structure of Mn ions and on the ferromagnetism. Our work may be helpful for further understanding the origin of ferromagnetism in GaN-based diluted magnetic semiconductors.  相似文献
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