Study On The Luminescene Properties Of Free-standing GaN-based LED Film

At present, there are mainly two kinds of methods to prevent crack and reduce tension of the silicon substrate Ga N based LED epitaxial film:one is the of graphics on silicon substrate,and the other is grow thick Al Ga N buffer layer,the two methods have their advantages and disadvantages.Although the graphic silicon substrate Ga N based LED has achieved mass production and is gradually accepted by the maket,but there are many scientific and technical issues to resolved,and a lot of research gaps worth to in-depth study. Among these issues, to clearly research the different micro zone photoluminescence and the stress state in a single pattern of Ga N-based LED films grown on patterned silicon substrate, the stress interaction between the buffer layer and the quantum well layer and the effects to dthe luminescent properties, these have important guiding significance to improve the quality and performance of the devices on silicon substrate epitaxial Ga N thin film.In this paper, different micro zone photoluminescence properties in a single pattern of Ga N-based LED film grown on patterned silicon substrate,nondestructive free-standing LED thin film after removel of the silicon substrate,and the free-standing LED films after reoveling Al N buffer layer were systematically studied. The photoluminescence spectrum is an important means to study the Ga N based LED, however, the silicon substrate is nottransparent substrate, it has some of the reflectance of visible light, epitaxial LED thin film on silicon substrate,its photoluminescence spectrum has obvious interference phenomenon,which brought great difficulties to the luminescence propertises of Si substrate LED. In this paper, using the characteristics of Ga N specific, researched a method to eliminate the interference in PL spectrum, this bring great convenience to accurate research luminescence properties on silicon substrate Ga N based thin film.The main research contents and conclusions are as follows:1.After removed the silicon substrate, the free-standing LED films bends to the substr ate direction in a cylindrical bending state. After removing the Al N buffer layer, the LED film would bend into flat.2.LED thin films on silicon substrate or removed silicon substrate, their PL spectrum have significant differences in different micro zone of the same graphics. When rem oved the Al N buffer layer, the PL spectrum tends to be consistent in the different mi cro zone of the same graphics.3.When the graphics silicon substrate GaN-based LED thin film removed silicon subs trate, the PL spectra would be apparent redshift at each micro zone. After further re moved Al N buffer layer, the PL spectra appeared different degrees of blueshift at e ach micro zone.4.Before and after removing the Al N buffer layer of the free-standing LED films,the Droop effectwill reveal some changes.5.Inserting a roughed Ga N film in the PL spectrum test system, the obvious interference phenomenon of PL spectrum of Ga N based film grown on silicon substrate will be eliminated completly.The results of eliminating PL interference are better than that reported in the literature.