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Yue-Bo Liu 《中国物理 B》2021,30(11):117302-117302
We report an abnormal phenomenon that the source-drain current (ID) of AlGaN/GaN heterostructure devices decreases under visible light irradiation. When the incident light wavelength is 390 nm, the photon energy is less than the band gaps of GaN and AlGaN whereas it can causes an increase of ID. Based on the UV light irradiation, a decrease of ID can still be observed when turning on the visible light. We speculate that this abnormal phenomenon is related to the surface barrier height, the unionized donor-like surface states below the surface Fermi level and the ionized donor-like surface states above the surface Fermi level. For visible light, its photon energy is less than the surface barrier height of the AlGaN layer. The electrons bound in the donor-like surface states below the Fermi level are excited and trapped by the ionized donor-like surface states between the Fermi level and the conduction band of AlGaN. The electrons trapped in ionized donor-like surface states show a long relaxation time, and the newly ionized donor-like surface states below the surface Fermi level are filled with electrons from the two-dimensional electron gas (2DEG) channel at AlGaN/GaN interface, which causes the decrease of ID. For the UV light, when its photon energy is larger than the surface barrier height of the AlGaN layer, electrons in the donor-like surface states below the Fermi level are excited to the conduction band and then drift into the 2DEG channel quickly, which cause the increase of ID.  相似文献   
2.
Yue-Bo Liu 《中国物理 B》2021,30(12):128102-128102
The uniform distribution model of the surface donor states in AlGaN/GaN heterostructures has been widely used in the theoretical calculation. A common and a triple-channel AlGaN/GaN heterostructure Schottky barrier diodes have been fabricated to verify the models, but the calculation results show the uniform distribution model can not provide enough electrons to form three separate 2DEGs in the triple-channel AlGaN/GaN heterostructure. Our experiments indicate the uniform distribution model is not quite right, especially for the multiple-channel AlGaN/GaN heterostructures. Besides, it is found the exponential distribution model possibly matches the actual distribution of the surface donor states better, which allows the 2DEG to form in each channel structure during the calculation. The exponential distribution model would be helpful in the research field.  相似文献   
3.
The effect of silver nanostructures prepared by nanosphere lithography on the photoluminescence(PL) properties of blue-emitting In Ga N/Ga N quantum wells(QWs) is studied. Arrays of silver nanoparticles are fabricated to yield a collective surface plasmonic resonance(SPR) near to the QWs emission wavelength. A large enhancement in peak PL intensity is observed, when the induced SPR wavelength of the nanoparticles on the QWs sample matches the QWs emission wavelength. The study proves that the SPRs could enhance the light emission efficiency of semiconductor material.  相似文献   
4.
We demonstrate the fabrication of hexagonal nano-pillar arrays at the surface of GaN-based light-emitting diodes (LEDs) by nanosphere lithography. By varying the oxygen plasma etching time, we could tune the size and shape of the pillar. The nano-pillar has a truncated cone shape. The nano-pillar array serves as a gradual effective refractive index matcher, which reduces the reflection and increases light cone. It is found that the patterned surface absorbs more pumping light. To compare extraction efficiencies of LEDs, it is necessary to normalize the photoluminescence power spectrum with total absorption rate under fixed pumping power, then we could obtain the correct enhancement factor of the photoluminescence extraction efficiency and optimized structure. The highest enhancement factor of the extraction efficiency is 10.6.  相似文献   
5.
The electrical properties of the structure of GaN grown on an Si (111) substrate with low-temperature (LT) A1N interlayers by metal-organic chemical-vapour deposition are investigated. An abnormal P-type conduction is observed in our GaN-on-Si structure by Hall effect measurement, which is mainly due to the A1 atom diffusing into the Si substrate and acting as an acceptor dopant. Meanwhile, a constant n-type conduction channel is observed in LT-A1N, which causes a conduction-type conversion at low temperature (50 K) and may further influence the electrical behavior of this structure.  相似文献   
6.
Surface patterning of p-GaN to improve the light extraction efficiency of GaN-based blue light-emitting diodes (LEDs) has been investigated. Periodic nanopillar arrays on p-GaN have been fabricated by polystyrene (PS) nanosphere lithog- raphy; the diameter of the nanopillars can be tuned to optimize the electrical and optical properties of the LEDs. The electroluminescence intensity of the nanopillar-patterned LEDs is better than that of conventional LEDs; the greatest en- hancement increased the intensity by a factor of 1.41 at a 20 mA injection current. The enhancements can be explained by a model of bilayer film on a GaN substrate. This method may serve as a practical approach to improve the efficiency of light extraction from LEDs.  相似文献   
7.
Surface patterning of p-GaN to improve the light extraction efficiency of GaN-based blue light-emitting diodes(LEDs) has been investigated. Periodic nanopillar arrays on p-GaN have been fabricated by polystyrene(PS) nanosphere lithography; the diameter of the nanopillars can be tuned to optimize the electrical and optical properties of the LEDs. The electroluminescence intensity of the nanopillar-patterned LEDs is better than that of conventional LEDs; the greatest enhancement increased the intensity by a factor of 1.41 at a 20 mA injection current. The enhancements can be explained by a model of bilayer film on a GaN substrate. This method may serve as a practical approach to improve the efficiency of light extraction from LEDs.  相似文献   
8.
Crack-free Ga N/In Ga N multiple quantum wells(MQWs) light-emitting diodes(LEDs) are transferred from Si substrate onto electroplating Cu submount with embedded wide p-electrodes. The vertical-conducting n-side-up configuration of the LED is achieved by using the through-hole structure. The widened embedded p-electrode covers almost the whole transparent conductive layer(TCL), which could not be applied in the conventional p-side-up LEDs due to the electrodeshading effect. Therefore, the widened p-electrode improves the current spreading property and the uniformity of luminescence. The working voltage and series resistance are thereby reduced. The light output of embedded wide p-electrode LEDs on Cu is enhanced by 147% at a driving current of 350 m A, in comparison to conventional LEDs on Si.  相似文献   
9.
The electrical properties of the structure of GaN grown on an Si (111) substrate with low-temperature (LT) AlN interlayers by metal-organic chemical-vapour deposition are investigated. An abnormal P-type conduction is observed in our GaN-on-Si structure by Hall effect measurement, which is mainly due to the Al atom diffusing into the Si substrate and acting as an acceptor dopant. Meanwhile, a constant n-type conduction channel is observed in LT-AlN, which causes a conduction-type conversion at low temperature (50 K) and may further influence the electrical behavior of this structure.  相似文献   
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