Electromechanical Coupling Properties Of GaN Nanobelt Based Piezoelectric Transistors

Recently,Micro-Electro-Mechanical System(MEMS)research tends to be mature,and MEMS devices are widely used in the market.Due to these advantages of high breakdown voltage,high thermal conductivity,corrosion resistance and radiation resistance,Chemical vapor deposition(CVD)was widely applied in the preparation of GaN nanomaterials,especially GaN nanobelts.In the report on GaN nanomaterials prepared by using CVD,the main researches focus on the single orientation and preparation of GaN nanomaterials and related properties.There are a few detailed studies have been reported on the influences of CVD parameters on GaN nanomaterials and electro-mechanical properties of GaN nanobelt piezoelectric Transistors transistors.In this thesis,the key influencing parameters of GaN nanobelts prepared by using CVD method were studied,and electro-mechanical properties of single GaN nanobelt by using atomic force microscopy(AFM)to measure piezoelectric coefficient,two-dimensional current image and I-V characteristics.In addition,the electrical properties of GaN nanobelt transistors were measured by using semiconductor parameter test analyzers.The main contents and results are as follows:(1)The CVD parameters were adjusted to study the critical influing parameters of GaN nanobelt.The experimental results showed that the source of germanium,the rate of temperature increase and the distance between them are indeed the key factors for the GaN nanobelts prepared by using CVD method.Piezoelectric coefficient of GaN nanobelt was measured by pressure force microscopy(PFM).and the maximum value of the piezoelectric coefficient of GaN nanobelt is 20 pm/V.(2)The two-dimensional current images of ingle GaN nanobelt were measured by using conductive atomic force microscope(C-AFM)under different loading forces.Both the edge defects of the GaN nanobelt and the larger values of the current caused by the contact position of the probe scanning appeared on the edge of GaN nanobelt.The I-V characteristics of single GaN nanobelt were measured by using conductive atomic force microscope(C-AFM)under different loading forces.The results show that different loading forces will produce different piezoelectric electric field,which will affect the current transport behavior of GaN nanobelts.In addition,the I-V characteristics on single GaN nanobelt force switch are studied.The experimental results show that the force-induced ol/off current ratio reaches 3.1×102.(3)The electrical characteristics of the GaN nanobelt transistors were measured by using a semiconductor test analyzer.The experimental results show that as the gate voltage Vg increases from-1 V to +2 V,the slope of the output characteristic curve gradually increases.The analysis results show that the GaN nanobelt have n-type semiconductor characteristics,and the prepared GaN nanobelt transistors are n-type depletion mode transistor...