Charge-Carrier Mobility in Diamond: Review, Data Compilation, and Modelling for Detector Simulations

TL;DR

Diamond charge transport is highly field- and temperature-dependent, with large reported variability in electron and hole mobilities and saturation velocities. The authors aggregate literature, compare TK, CT, and a new PW mobility description, and show that electrons are best described by PW across broad fields while holes are best described by CT, once source-dependent normalization is accounted for. They reveal a systematic alpha-vs-laser offset in drift velocities and quantify temperature scalings near room temperature, presenting parameter sets for detector and device simulations. The work highlights the need for wide-range TCT campaigns and offers concrete guidance for model choice and experimental design to enable consistent, predictive modeling of charge transport in intrinsic diamond. This has practical implications for high-rate, high-temperature radiation detectors and diamond-based electronics. $v_d(E)$ behavior is captured by equations such as $v_d = v_s rac{E/E_c}{(1+(E/E_c)^{eta})^{1/eta}}$ in CT/TK, while PW combines a linear low-field regime with a high-field CT-like saturation, facilitating robust device simulations across varied conditions.

Abstract

Reported electron and hole mobilities, and their saturation velocities, in diamond span orders of magnitude across the literature. We attribute this dispersion primarily to (i) the electric-field window probed in TCT measurements, (ii) the choice of mobility model, and (iii) the excitation source (alpha, laser, or electron). Using an aggregated literature dataset, we benchmark the Trofimenkoff and Caughey-Thomas parameterisations together with a new piecewise model for both conduction- and valence-band transport. For electrons, the piecewise model provides the best global description over a broad electric-field range and is shown to arise as the room-temperature limit of a more general superposition framework that explicitly incorporates intervalley repopulation in the conduction band. For holes, the Caughey-Thomas model remains the statistically preferred description, in line with the absence of a strong repopulation effect in the accessible data. Furthermore, we demonstrate a systematic source dependence (alpha versus laser) and quantify its impact on fitted mobility and saturation-velocity values. We provide temperature scalings over narrow intervals around room temperature and recommend parameter sets for implementation in device and detector simulation frameworks. Together, these results reconcile much of the apparent inconsistency in the literature and offer clear guidance for model selection, experimental design, and device-level simulation of charge transport in intrinsic diamond.

Figures (11)

• Figure 1: (a) Schematic of a TCT setup used to measure charge carrier mobility in diamond. (b) Idealized TCT waveforms showing the transient current response. The gold trace corresponds to complete charge collection. The carrier transit time is extracted from the full width at half maximum (FWHM). The red trace corresponds to incomplete drift, where the charge cloud does not reach the collecting electrode and the trailing edge exhibits no cusp.
• Figure 2: Drift velocity $\mathrm v_{d}$ and effective mobility $\mu_\mathrm{eff}$ versus electric field $\mathrm E$ (schematic). (a) $\mathrm v_{d}$--$E$ characteristics showing a linear (left) regime and a velocity-saturation (right, transparent) regime separated by the critical field $\mathrm E_{c}$. The onset and termination of the saturation plateau bound the range of saturation velocities $\mathrm v_{s}$ for electrons (blue) and holes (red). (b) $\mu_\mathrm{eff}$--$E$ characteristics illustrating the decrease of $\mu_\mathrm{eff}$ with increasing field. $\mu_\mathrm{eff}$ remains approximately constant up to $\mathrm E = E_{c}$, after which it declines as velocity saturation sets in. Horizontal lines indicate the low-field mobilities $\mathrm \mu_{0,e}$ and $\mathrm \mu_{0,h}$. Details are provided in the main text.
• Figure 3: Transient-current signals (holes) at 34 V for varying laser intensities, illustrating the transition from SCFC to SCLC currents at $\mathrm{Q_{inj}}=34$ pC. Figure adapted from Isberg2011.
• Figure 4: Data grouping structure: Group 1 (experiment-wise) and Group 2 (pooled-data).
• Figure 5: Selected (pink) and rejected data used for model evaluation of (a) electron and (b) hole transport.