Gallium nitride emitting devices preparation and properties

Abstract

GaN:Zn//Al₂O₃ electroluminescent devices have been obtained with a wide range of emitted colours (blue, green, yellow and red) ; theses devices have high potential since external quantum efficiencies greater than 1 % and power efficiencies of about 10⁻³ have been reported. On the other hand, from the literature it seems that each colour is obtained randomly, since apparently the same method of preparation is used. We show that the properties of GaN:Zn (conductivity type, cathodoluminescence (peaks and efficiency)) can not be related uniquely to the partial pressure of zinc during the growth, but it is also necessary to take into account the partial pressure of HCl and the thickness of the π layer in order to obtain a satisfactory representation of these properties. From this knowledge, one can deduce the different parameters for growing layers for devices and control their properties. The device fabrication consists of the deposition of a Zn doped thin layer, which is nearly insulating but with p tendency (π layer), onto a Zn doped n type layer. It is demonstrated that the characteristics of the devices (I(V) curves, electroluminescent peaks and efficiencies are related to the characteristics of the π layer and on the transition from n to π. Blue LEDS with characteristics very similar to p-n junction characteristics have been obtained.