Abstract: Two samples of InGaN/GaN MQW blue LED epitaxial wafers were grown under different conditions by CCS-MOCVD system. The two samples were tested and analyzed from epitaxial wafers to fabricated LED dies and packaged devices. The performance of B (forward voltage, light intensity, reverse leakage current, wavelength uniformity, FWHM, etc.) is better than that of sample A. INTRODUCTION Group III-V nitrogen compounds InN, GaN, AIN and their alloys have a band gap width from 1.9 eV to 6.2 eV covering the range of visible and ultraviolet light spectra. GaN material series is an ideal short-wavelength light-emitting device material. The research and application of GaN materials is the frontier and hot spot of global semiconductor research. The blue and violet LEDs on the market are all made of GaN-based materials. GaN is a very stable compound and a hard high melting point material. It is also a direct-transition wide band gap semiconductor material. It has good physical and chemical properties, high electron saturation rate, good thermal conductivity, large forbidden band width and dielectric constant. Small features and strong anti-irradiation ability, can be used to prepare high-power devices with good stability, long life, corrosion resistance and high temperature resistance. Currently widely used in optoelectronics, blue LED, violet detector, high temperature and high power devices and high Photoelectric devices such as frequency microwave devices. Second, the experiment This article uses the vertical CCS-MOCVD system produced by Thomas Swan. Third, testing and analysis From the growth oscillation curve, there is a very big difference. IV. Results and Discussion InGaN/GaN MQW blue LED epitaxial wafers were grown using the CCS-MOCVD system. Through this experiment, the epitaxial wafers of two samples were analyzed and tested. It was found that the length of the ammoniation time of the substrate and the stoichiometric ratio of the amount of gallium and ammonia in the GaN buffer layer were the main factors affecting the performance of the InGaN/GaN MQW LED epitaxial wafer. factor. If handled well, the properties of the grown epitaxial wafer include crystal quality, forward voltage, light intensity, reverse leakage current, wavelength uniformity, FWHM, etc., and the performance of the chip and device are greatly improved and improved. Best selling best quality plastic Electric Egg Mixer. It use for mixing eggs and dough. Can choose copper clade aluminum motor or full copper motor. With two egg beaters and two dough hooks. Generally have five speeds to seven speeds, easy to operate. In difference speed can effect the batter you want. Some model can fix on the bowl. That can save your strength when you have to mix for a long time. Have ejection button, easy to release the beaters and the hooks. Can clean easily after use. Small size and detachable, convenient and store easily. Electric Hand Egg Mixer,Egg Mixer,Hand Egg Mixer,Electric Egg Mixer,Kitchenaid Hand Mixer,Kitchenaid Hand Egg Mixer Jiangmen Yingxiang Motor Manufacturer Co., Ltd. , http://www.yingxiang-blender.com
Abstract: InGaN/GaN MQW and Bluelight LED extension chip are made in different conditions under CCS-MOCVD system. The essay gives an the result of test and analysis on the two items from LED core to encapsulation. After comparison it is found that item B Is better than A on terms of forward current, light intensity, reverse-leakage current, uniformity of wavelength and FWHM, etc.
The preparation of high quality GaN-based materials and thin film single crystal materials is a prerequisite for the development and development of luminescent epitaxial materials and device properties. At present, no company on the market can produce two-inch high-quality GaN single crystal substrates. Even with GaN single crystal substrates, the price is quite expensive. Most of the substrates used today are sapphire (Al2O3). Although it has a lattice mismatch of 13.8% with GaN, the GaN thin film material grown on the sapphire substrate has a very high dislocation density. The cost is low, the price is low, the process is relatively mature, and it has good stability at high temperatures.
The purpose of this paper is to study the effects of low temperature growth of GaN buffer layer on epitaxial wafer properties (forward voltage, light intensity, reverse leakage current, wavelength uniformity, FWHM, etc.), chips and devices under different conditions.
In this experiment, GaN was grown at low pressure (100 Torr). The substrate material used was Al2O3 (0001) plane, trimethylgallium (TMG), trimethylindium (TMIn) and lanthanum (NH3) were used as Ga sources, respectively. In source and N source, silane (SiH4) and Cp2Mg are n, p type dopants, respectively, and the carrier gas is high purity H2 and N2. The growth process was as follows: First, the substrate was heated to 10500 C under an atmosphere of H2, baked for 5 minutes, and then cooled to 5300C. Sample A was nitrided with 2500 ml/m ammonia gas for 120 seconds to regenerate the buffer layer. The flow rates of NH3 and TMG were 1300 ml/min and 15 μmol/min, respectively; Sample B was nitrided with 5000 ml/m ammonia for 60 seconds. The buffer layer is further grown, and the flow rates of NH3 and TMG are 5000 ml/min and 30 μmol/min, respectively; both samples are grown with a GaN buffer layer having a thickness of 25 nm, and the temperature is raised to recrystallize the buffer layer to grow the undoped GaN single crystal layer and Si-doped n-GaN single crystal layer, 5 cycles of InGaN/GaN MQW, Mg-doped p-AlGaN/GaN single crystal layer.
From the surface topography of the epitaxial layer, the surface morphology of sample A is clearly not as good as that of sample B. There are many small protrusions, pinholes and hexagonal crystals on the surface of sample A, while the surface of sample B is very fine, and the gloss and flatness are very good.
A rapid test was performed on the two epitaxial wafer samples. The two probes were directly in contact with the epitaxial wafer. Sample A found that the light emitted by the epitaxial wafer was unstable, and the leakage current was large, and the result of the sample B was ideal. The peak photoluminescence peak wavelengths of the two samples were 473.5 nm and 468.7 nm, respectively, and the FWHM was 32.9 nm and 21.3 nm, respectively, and the epitaxial wafer wavelength uniformity sample B was better than the sample A. After testing the two samples into a die, it was found that the forward voltage of sample A (at 20 mA) was around 3.5 V, the reverse leakage current was large, the reverse voltage was 0.4 μA at 5 V, and the light intensity was between 20 mcd and 35 mcd. The forward voltage of sample B (at 20 mA) is about 3.3 V, the reverse voltage (at 10 μA) is above 12 V, and the light intensity is between 35 mcd and 50 mcd. The reason for the poor surface quality and large leakage current of the sample A crystal in this paper is attributed to the fact that the gallium flow rate and the ammonia gas flow rate do not reach a good stoichiometric ratio and the ammoniation time are different when the GaN buffer layer is grown.