The Ultraviolet Photodetection Properties Of Gallium Nitride/Silicon Nanoporous Pillar Array

The ultraviolet photodector are playing important roles in a variety of fields such as industrial and agricultural production,environmental monitoring and protection,and national defense industry.Semiconductors was widely used in the field of ultraviolet photoelectric detection with the development of semiconductor materials.The silicon as the typical representative of the first generation of semiconductors materials was applied to the field of UV photodetector.UV-enhanced silicon photodiode was a pioneer of solid detectors,and it has had a technically mature.But the silicon detector is disturbed by visible light noise,which need a filter to pass the visible light,and the silicon detector was easy to age and shorten the service life of using.In addition,silicon is an indirect bandgap semiconductor material,which made silicon optoelectronic devices had a low light quantum response efficiency.In recent years,GaN and ZnO as the typical representative of the wide bandgap semiconductor materials had been rapid development in the preparation and device technology,especially based on GaN homo/hetero-junction of optoelectronic devices such as,short wavelength light-emitting diodes,laser diodes and solar cells etc.GaN was direct bandgap semiconductor materials with high optical response quantum efficiency and the band gap width was about ~3.34 eV,which corresponding intrinsic absorption and emission wavelengths were in the ultraviolet region.At the same time,GaN had the nice chemical and stability,high thermal conductivity,anti-radiation ability and so on.The above properties of GaN indicate that it is expected to be an ideal material for the preparation of novel high performance UV detectors.In our work,we report that utilizing silicon nanoporous pillar array(Si-NPA)as substrates,nanoheterojunction arrays based on GaN/Si-NPA were prepared by a chemical vapor deposition method(CVD)through changing the deposition condition,and the surface morphology,chemical composition and photoluminescence property were characterized.By depositing the top transparent ITO electrode and the back Ag electrode,a prototype photodector with a device structure of ITO/GaN/Si-NPA/sc-Si/Ag was prepared and its photodetection properties were measured.The control the preparation conditions of GaN pursuing a better conditions to make a optimized UV detectors.Our work carried out a research work as below.1)We prepared a Si-NPA by hydrothermal synthesis method and structured a GaN/Si-NPA nano-heterojunction by CVD method.Si-NPA is a silicon nanometer-micrometer hierarchical structure characterized by a regular array of well separated,micron-sized and highly nanoporous silicon pillars.The unique microstructure had a special performance due to the quantum confinement effect,result in the indirect band gap semiconductor Si transforming into a quasi-direct band gap,and the band gap change from ~1.1 eV to ~2.6 e V.First,a layer of metal Pt was deposited as a catalyst for grown GaN on the surface of Si-NPA,and GaN/Si-NPA nano-heterojunction was prepared by CVD method.The ITO/Si-NPA/sc-Si/Ag UV detection prototype device was formed after the ITO transparent layer was sputtered as the top electrode and the Ag was deposited on sc-silicon by v vacuum evaporation.2)We controled the temperature of deposited GaN to study the effect of deposition temperature of UV detection performance of GaN/Si-NPA,and then characterizing the phase analysis and morphology of GaN/Si-NPA.Then,the UV detection performance of the response range and response/recovery speed were tested of GaN/Si-NPA.The response was divided into two bands: ultraviolet and blue.The optimized preparation temperature of GaN was 950?.3)We controled the time deposited of GaN to study its effect for UV detection performance of GaN/Si-NPA,and analyzed the characterizing the phase and morphology of GaN/Si-NPA.And study the influence of UV detection prototype by GaN deposition time.Then,the UV-response test of the prototype device was carried out.It was found that the device with 20 min deposition was optimized.At the same time,in order to verify that the blue light came from the substrate,the ITO/Si-NPA/sc-Si/Ag structure was prepared to finish blue light response test.4)The effect of ammonia flow on the UV detection of GaN/Si-NPA was investigated.The above studies showed that the preparation conditions of GaN were optimized when the conditions of GaN preparation were 950 ?,deposition time was 20 min and ammonia flow rate was 3 sccm.The spectral response range of the UV detector is 280-380 nm,the highest response at 0 V bias is ~0.15 mA / W,and the response/recovery time is ~0.04 s.Our research results might be meaningful for developing novel type ultraviolet photodetectors made of Si-based GaN materials.