Depletion-limited Effective Hall mobility in Micrometer-Scale High-Purity Germanium Crystals
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| Format: | Preprint |
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2025
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| author | Budhathoki, Narayan Mei, Dongming Bhattarai, Sanjay Chhetri, Sunil Dong, Kunming Panamaldeniya, Shasika Prem, Athul Warren, Austin |
| author_facet | Budhathoki, Narayan Mei, Dongming Bhattarai, Sanjay Chhetri, Sunil Dong, Kunming Panamaldeniya, Shasika Prem, Athul Warren, Austin |
| contents | Electrostatic effects can strongly constrain charge transport in thinned high-purity germanium (HPGe), with direct implications for radiation detectors and Ge-based electronic and quantum devices. We report a systematic experimental characterization of the thickness-dependent effective Hall mobility in bulk-grown, detector-grade HPGe at room temperature using Hall-effect measurements on n- and p-type samples sequentially thinned from 2.7~mm to 7~\textmu m. The intrinsic bulk carrier mobility remains thickness independent in this regime; the observed reduction in Hall-extracted mobility arises from electrostatic surface depletion that reduces the electrically active conducting thickness. The thickness-dependent data are accurately parameterized by an empirical extended-exponential relation, $μ(t)=μ_{0}[1-\exp(-(t/τ)^β)]$, where $τ$ is a characteristic electrostatic length scale. Comparison with boundary-scattering and depletion-based models shows that Fuchs--Sondheimer scattering is negligible, while electrostatic depletion dominates the transport behavior. The hierarchy $λ_{D}<τ\lesssim W_{0}$ directly links the apparent mobility reduction to long-range screening and near-surface electric fields. These results yield a simple design guideline: maintaining thicknesses $t\gtrsim 3τ$ preserves near-bulk transport, whereas thinner structures operate in a depletion-controlled regime with strongly reduced effective conductivity. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_20842 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Depletion-limited Effective Hall mobility in Micrometer-Scale High-Purity Germanium Crystals Budhathoki, Narayan Mei, Dongming Bhattarai, Sanjay Chhetri, Sunil Dong, Kunming Panamaldeniya, Shasika Prem, Athul Warren, Austin Applied Physics Electrostatic effects can strongly constrain charge transport in thinned high-purity germanium (HPGe), with direct implications for radiation detectors and Ge-based electronic and quantum devices. We report a systematic experimental characterization of the thickness-dependent effective Hall mobility in bulk-grown, detector-grade HPGe at room temperature using Hall-effect measurements on n- and p-type samples sequentially thinned from 2.7~mm to 7~\textmu m. The intrinsic bulk carrier mobility remains thickness independent in this regime; the observed reduction in Hall-extracted mobility arises from electrostatic surface depletion that reduces the electrically active conducting thickness. The thickness-dependent data are accurately parameterized by an empirical extended-exponential relation, $μ(t)=μ_{0}[1-\exp(-(t/τ)^β)]$, where $τ$ is a characteristic electrostatic length scale. Comparison with boundary-scattering and depletion-based models shows that Fuchs--Sondheimer scattering is negligible, while electrostatic depletion dominates the transport behavior. The hierarchy $λ_{D}<τ\lesssim W_{0}$ directly links the apparent mobility reduction to long-range screening and near-surface electric fields. These results yield a simple design guideline: maintaining thicknesses $t\gtrsim 3τ$ preserves near-bulk transport, whereas thinner structures operate in a depletion-controlled regime with strongly reduced effective conductivity. |
| title | Depletion-limited Effective Hall mobility in Micrometer-Scale High-Purity Germanium Crystals |
| topic | Applied Physics |
| url | https://arxiv.org/abs/2511.20842 |