Study On Synthesis And Properties Of Boron-doped Single Crystals And Polycrystalline Diamond

As an important functional material,diamond has many excellent characteristics,such as superhardness,high thermal conductivity,high electron hole migration speed and wideband gap,high optical transmittance and chemical inertness.Through semiconductor doping,p-type or n-type conductive diamond can be obtained,which has been widely used in the semiconductor field.The most important doping of p-type diamond is boron doping.The influence of boron doping on the growth and physical properties of diamond is an important factor to determine the performance and application of diamond semiconductor devices.In This paper,boron-doped diamond single crystal film was grown on the HTHP diamond single crystal substrate with homogeneous epitaxy by MPCVD.By extending the growth time and increasing the flow rate of boron source,the boron-doped diamond films with single crystal and polycrystal coexisted were obtained.We researched the electrical properties of single and polycrystalline crystals with changing the hydrogen and oxygen terminals.The main results are as follows:(1)Boron doped diamond single crystal thin films grown in a short time had smooth surface and good quality.The maximum carrier concentration could reach 10¹⁹?10²¹cm^-3,and the maximum mobility could reach 100cm²·V^-1·s^-1.The activation energy of boron was calculated to be in good agreement with the theoretical value(0.37 eV)by testing the Hall effect.(2)TheV-shaped columnar growth characteristics of polycrystals could be observed in the films with the coexistence of polycrystals and single crystals.The boron concentration estimated by Raman spectroscopy was10²⁰?10²¹cm^-3,which proved that the boron concentration of polycrystals is higher than that of single crystals under the same growth conditions.(3)Au and boron-doped single crystal diamond contact can be modulated by surface terminal,the hydrogen terminal is ohmic contact,the oxygen terminal is Schottky contact.The ?-? curves of polycrystal and single crystal with oxygen terminal show typical rectification characteristics.This work provides a new idea for regulating the growth of diamond single crystal and polycrystal structure,improving the contact of diamond electrode,and designing new diamond electronic devices.