The Study Of Improvements On Epitaxial Growth Technology On Gan Based LED

LED has the characteristics of light weight, thin, short as well as small size. Itis impact-resistance after encapsulation and has a long life time. It is widely used inmany applications. People have paid more and more attention to its reliabilities. LEDwith GaN materials has become commercial produced, but the research on GaNmaterials and LED is still going on. The emphases are to improve the quality of theGaN materials and the quantum efficiency as well as improve its ESD. The aim of thework in this dissertation is to improve its photoelectric properties. For example,improving the brightness, reducing the forward voltage as well as improving the ESD.The main aspects are as follows:(1) The basic structure and the growth parameters of every layer were described indetail in the dissertation. We pointed out the main aspects affecting the reliabilities ofLED after theoretical analysis.(2) We took the experiments of adding Indium to the barrier layers. This reducedthe dislocation density and the number of non-radiative centers. The polarization fieldproduced by the stresses of lattice mismatch between the barriers and the wells isreduced. This improved the brightness of the LED, reduced the leakage passage andimproved the ESD.(3) With the experiments of adding Indium to the barrier layers, we tookoptimization and improvement on the growth structure of epitaxial wafers. We add5nmp-InGaN cap layers above the p-GaN layer, which increased the hole concentrations andcurrent spreading ability. The forward voltage has been reduced by10%in comparsionwith the traditional samples. Furthermore, this reduced the agglomeration of the currentand the electric field. And the ESD property has been improved.(4)After the above two improvements, we added n-AlGaN layer to the ESD andthis formed the n-AlGaN/GaN heterojunction. Therefore, the carriers were restricted,Which made the electronics restricted in the modulation-doped superlattices and formedthe two-dimensional electron gas. The current spreading ability was finally improvedand avoided the damage which is caused by the high density of local current. So theESD of LED was greatly improved.The characterization means we used in the experiments are XRD. PL. SEM etc.