High carrier mobility in ultrapure diamond measured by time-resolved cyclotron resonance

Abstract

We have performed time-resolved cyclotron resonance measurements in ultrapure diamond crystals for the temperature range of T=7.3–40 K and obtained the temperature-dependent momentum relaxation times based on the cyclotron resonance widths for optically generated electrons and holes. The relaxation time follows a T−3/2 law down to 12 K, which is expected for acoustic-phonon scattering without impurity effect because of the high purity of our samples. The deviation from the law at lower temperatures is explained by the impurity scattering and the breakdown of the high-temperature approximation for the phonon scattering. We extract the carrier drift mobility by using the directly measured effective masses and the relaxation times. The mobility at 10 K for 600 ns delay time after optical injection is found to be μe=1.5×106 cm2/V s for the electrons, and μlh=2.3×106 cm2/V s and μhh=2.4×105 cm2/V s for the light and heavy holes, respectively. These high values are achieved by our high-sensitivity detection for low-density carriers (at <1011 cm−3) free from the carrier-carrier scattering as well as by the suppression of the impurity scattering in the high-purity samples.

Intrinsic Carrier Parameters and Optical Carrier Injection Method in High-Purity Diamonds

“…As discussed in Ref. [23], these values were larger than the values calculated by modified Erginsoy's formulas, β e = (3.4 n A a A + 20 n D a D ) ℏ / m e * for the electron [39] and β h = (20 n A a A + 3.4 n D a D ) ℏ / m h * for the hole, where a A (D) is a Bohr radius and n A (D) is the concentration of acceptors (donors). This fact indicates that the estimated n I a I (I = A, D) were smaller than those in the actual situations probably owing to the too much simplified estimation of the Bohr radius by the hydrogenic model.…”

“…[25]. Figure 9b shows the CR spectra at 7.3, 10, 20, 30, and 40 K taken at a delay time of 1 μs after the laser pulse with averaging window for ±40 ns [23]. The four peaks were separately observed up to 20 K and the width broadened with increasing temperature.…”

“…In this chapter, our recent experimental contributions to clarify the basic and intrinsic carrier parameters in a diamond will be introduced [21][22][23][24][25][26][27]. The measurement has been performed by a time-resolved cyclotron resonance method under optical carrier injection in pure diamond crystals.…”

“…Temperature variation of temporal curves at 0.16 mT (a) and spectrum at the delay time 1 μs averaged for ±40 ns (b), adapted from Ref [23]…”

Electron mobility in (100) homoepitaxial layers of phosphorus-doped diamond

“…21 For both orientations, they remain large compared to those in ultra-pure diamond found using the time of flight (D a = 12 eV and D f /g = 4×10 8 eV cm −1 ) 30 or time-resolved cyclotron resonance (D a = 8.7 eV). 31 There are different scattering mechanisms in the layers. The neutral impurities have a very limited effect for all samples in the whole temperature range.…”