Transport properties of electron-beam and photo excited carriers in high-quality single-crystalline chemical-vapor-deposition diamond films

Abstract

We have investigated transport properties of carriers excited in high-quality homoepitaxial diamond (100) films by 5.6eV photons or 15keV electrons. The high-quality single-crystalline diamond films were homoepitaxially grown on type-Ib diamond substrates at a rate of 2.5μm∕h by high-power microwave-plasma chemical-vapor-deposition (MPCVD). In cathodoluminescence (CL) measurements, strong free-exciton recombination emissions were observed at room temperature from the almost whole specimen surface, indicating the grown films have substantially high quality. It is found through an analysis of the visible emission band originating from the type-Ib substrate that decay constants estimated for excited carriers were ∼5μm in the depth direction. This is consistent with the fact that the intensity of spotlike CL images varied with an exponential function of the lateral length. From transient photocurrent measurements using ultrashort pulse laser excitations, decay times τ for the present high-quality diamond were estimated to be 15 and 100ns for electrons and holes, respectively. Charge collection distances at an electric field E of 830V∕cm were deduced to be ∼190μm and over 1.2mm for electrons and holes, respectively. The former may give a high electron drift mobility of μ∼1600cm2∕Vs while the diffusion coefficients estimated for electrons are 55±14cm2∕Vs, which is comparable with or even higher than those of Si. These physical quantities demonstrate high quality of the diamond films grown by means of the high-power MPCVD method.

Diamond PN/PIN Diode Type Electron Emitter with Negative Electron Affinity and Its Potential for the High Voltage Vacuum Power Switch

“…The total photoelectron yield (TPY) for path I is proportional to the diffusion length of free electrons within the sample, which is at least a few micrometers in high quality intrinsic diamond samples [35]. Comparison of the TPY from path I and path II shows the onset of electron emission from the bulk into the vacuum as illustrated in Fig.…”

Crystallite size dependent carrier recombination rate and thermal diffusivity in undoped and boron doped CVD diamond layers

“…1 Introduction Carrier and thermal dynamics in diamonds are usually investigated at high photoexcitation conditions using above the bandgap quantum energies (hn > E g ¼ 5.5 eV) for carrier injection. The determined carrier lifetimes of 0.14-3.3 ns in HPHT and CVD grown diamonds [1,2] revealed a correlation between the carrier lifetimes and the nitrogen density, suggesting that nitrogenrelated defects act as main carrier recombination centers in diamond [3,4].…”

Development of a TOF measurement system of charge carrier dynamics in diamond thin films using a UV pulsed laser

“…They used polycrystalline diamond thin films with two parallel electrodes whose gap was 1mm, and laser irradiation was applied uniformly to the region between the electrodes. After this research, endeavor on measuring charge carrier transport characteristics for diamond films has been continued [12][13][14][15][16][17]. All these system adopted uniform irradiation between electrodes.…”