GaN On Silicon Resonant Gratings For Sensing Applications

With the rapid development of micro and nano processing technology, making the preparation of nanostructured devices a reality. In recent years, GaN-based grating devices has become one of the hot research. GaN is a direct bandgap semiconductor with remarkable piezoelectric and favorable optoelectronic properties. It is a temperature tolerant and radiation-hardened material and chemically inert to many corrosive chemicals, making it a promising material for fabricating sensor components and multi-sensing platforms that operate within a harsh environment.By the aid of software Rsoft, all parameters of suspended GaN gratings are calculated.According to the simulation results, the parameters of the gratings are designed and optimized. The software is based on rigorous coupled-wave theory(RCWA) method.This paper design the nanofabrication process steps, combine with silicon and nitride processing technology and the back thinning technology to fabricate the suspended membrane GaN gratings.Suspended GaN gratings are realized on a GaN-on-silicon platform. In order to achieve fully suspended membrane GaN gratings, silicon substrate material at the bottom of the GaN layer is completely etched away. Thus, suspended GaN gratings are completely surrounded by low refractive index of air, to satisfy the total reflection condition, light is confined within the grating layer, when the phase matching can produce significant resonance effects. This paper incorporates back thinning process, the thickness of the GaN membrane is thinned, which makes the suspended devices have low loss, high reflectivity, excellent resonator properties and other characteristics. In particular, it is shown that the resonant peaks of suspended GaN gratings are sensitive to the refractive index of the adjacent dielectric medium, which gives the capacity to develop such gratings as the template to create refractive index sensors which can be used for diverse applications.Angular resolved reflectance measurements experimentally demonstrate that the measurement results agree well with the simulation results.