Research On Etching GaN,P-type Ohmic Contact And Fabrication Of GaN LED

GaN has been extensively investigated for electronic and optoelectronic application, especially for GaN light emitting diodes(LEDs). Recently, tremendous progress has been achieved in GaN-based blue and green LED, which has a lot of attractive characteristics, such as little cubage, short response time, high efficiency, long lifetime, explosion resist etc. It can be widely used in the fields of large color display, traffic lights, LCDs' light source, fiber communication and so on. In this paper, we discuss Cl-based inductively coupled plasma(ICP) etching GaN and fabrication of p-type ohmic contact, especially the former. Besides we show the process flow of GaN LED. Following is the details:ICP etching of GaN was performed in a home-made equipment ICP-98C using Cl-based gases. It showed that the characteristics of the samples etched by Cl₂/He were better than that etched by Cl₂/Ar. When etching conditions were ICP power=500W, dc bias=180V, Cl₂/He=32sccm/8sccm, the surface roughness RMS was 0.36nm, lower than using Cl₂/Ar in the same conditions. We also investigated how the etch conditions such as different ICP power, dc bias, total flow and Cl₂:He ratio affects etch rate and surface roughness.Ni/Au was used as p-type ohmic contact. We tried different annealing temperature and thickness of Ni/Au, and got that 500 °C is the most suitable annealing temperature; Ni(10nm)/Au(10nm) is the most suitable thickness. Ni(10nm)/Au(10nm) was deposited on p-GaN by electronic beam evaporation,, then annealing in Oxygenat 500℃ for 5min. The specific contact resistivity(ρ_c) is 4.7 × 10^-5 Ω ? cm², and thelight transmittance is 75%.Ti(20nm)/Al(20nm)/Ni(20nm)/Au(100nm) was used as n-type ohmic contact,...