The Effects Of Different Barrier Structures On Properties Of The GaN-Based Green LED Film On Si Substrate

LED based on GaN, with its controllable panchromatic spectrum as well as excellent physical and chemical properties, has broad application prospects in a variety of areas such as lighting, backlighting and has gradually become the new generation of green illumination photosource. The current the mainstream technology program of LED illumination is the "blue LED + yellow phosphor" synthetic white LED,although you can get a higher luminous efficiency, isochromatic quality such as the color warm and the colored index is not good. In order to obtain a high-quality LED lighting in the true sense, white light requires a full LED mixed light, namely the use of red, green, blue three primary color LED(RGB) to obtain white light,so that you can achieve the perfect combination of low color temperature, high color rendering index as well as high efficiency. At present, the luminous efficiency of green light LED is far behind the blue and red LED,it is called "Green gap" in the academic circles, which has become a main technical bottlenecks to achieve RGB white light sources. Therefore, further advancing the green light LED quantum efficiency becomes a hot topic the field of LED in recent years. The large lattice mismatch between the barrier and well in the quantum well will cause large stress, which has obvious effects on optical and electrical properties of the Green light LED, but there has been no unified cognition. This article study barrier structure’s of silicon substrate green light LED effects on many characteristics such as stress,optical and electrical properties, the junction temperature characteristics and aging characteristics. The following research results:1)Using high-resolution x-ray diffraction(HRXRD),test reciprocal space mapping with(10 1 5) face non-symmetric diffraction of three different barrier structures(barrier including InGaN, barrier including AlGaN,the full GaN barrier)green LED epitaxial film of GaN-based on Si substrate. Characterize qualitatively the stress state of three quantum well structure, the results showed that the introduction ofInGaN and Al GaN barrier layer can obviously reduce the tensile stress in quantum well of green LED, in which when introducing InGaN the tensile stress is smallest.2) The three barrier structures of green LED epitaxial films of GaN-based on Si substrate wafer into the chips with the vertical structure and study the variable temperature electroluminescence properties(VTEL), the results show that: At the same temperature, with the increase of current density, EL peak wavelength of three kinds of structure are the blue shifting,but they are different in degree. when the ambient temperature is low temperature-13 K, with increasing current density,there is a bigger amount of blue shifting including AlGa N in barrier than the entire GaN barrier,the quantity of blue shifting is similar between the entire GaN barrier and barriers including InGaN. When the environment temperature is 300k(room temperature),the quantity of blue shifting is also different, the relations are: the entire GaN barrier is bigger than barrier containing AlGaN, barrier containing AlGaN is bigger than barrier containing InGaN. The quantity of wavelength in blue shift is related to the band bending caused by the quantum confined Stark effect(QCSE), the quantity of blue shift is smaller, the band bending is smaller. Thus, compared to the entire GaN barrier, the introduction of AlGaN and InGaN in the barrier can effectively reduce the QCSE, especially the introduction of InGaN barrier. It is consistent fully with the above stress relationship caused three different barrier structures in quantum wells of the green light LED.3) On the above three kinds of green light LED chips with different structure under room temperature, 500 mA aging for 500 hours, the light attenuation of three kinds of devices with different the barrier structures is relatively small, the entire GaN barrier to 2.47%, the barrier containing AlGaN to 5.33%, the barrier containing InGaN to 3.56%, their light attenuation may differ from the structure of quantum wells resulting from internal stress is different. The variation of turn-on voltage and the operating voltage is small; the maximum difference is respectively about 0.01 V and 0.1V.4) The junction temperature of three kinds of the green LED chips with the vertical structure and different barrier structures was studied, through a seriesmeasurement of temperature coefficients under the different currents from small to large,The conclusions obtained: The deviation of coefficient of temperature under the low current is larger, its reason is that there are the leakage channels in the chips,under low current,the ratio of leakage current occupying the test current is significant,this make a major impact on the junction temperature coefficient; The deviation of coefficient of temperature under the large current is smaller, the reason is,the leakage current is saturated for the large current test and accounts for a very small proportion of the test current. Based on the above judgment, the correct way to test junction temperature of green LED chips has been set up. Further, through this method characterize junction temperature rising characteristics of three kinds of barrier structures of green light LED chips, the results showed: It is smallest including InGaN in barriers of green light LED, the fllowing is the entire GaN barrier and the next is including AlGaN in barriers.5) Through controlling external stress of green light LED of GaN-based on Si substrate, study and analyze variations of d the EL Spectra with the strain, the results show that: In the annealing process, the tensile stress of GaN decreases gradually for green LED epitaxial films of GaN-based on Si substrate, compressive stress of quantum wells increases, which leds to the increasing of piezoelectric effect in quantum well and quantum limit Stark effect(QCSE), some phenomenons such as that chip parameters with the external stress becomes small, light power is down, half peak width increases and wavelength increases. This further certifies that decreasing the tensile stress of green light quantum well is helpful to improve the photoelectric properties.6) In conclusion, reducing tensile stress of quantum well with green light LED is beneficial to improve the photoelectric performance, and introducing In GaN and AlGaN in barrier can effectively reduce the tensile stress in green light quantum. All in all, InGaN introduced the green LED structure has best performance, mainly the stress is smallest in quantum well,the amount of blue shifting is smallest with increasing current density at room temperature and has the minimum junction temperature rising, stable photoelectric parameters in the process of aging. The aboveresearch results have a certain experimental and theoretical value for further enhancing the photoelectric properties of green LED.