Investigation of the electrical conduction mechanisms in P-type amorphous germanium electrical contacts for germanium detectors in searching for rare-event physics

• Main Authors: S. Bhattarai, R. Panth, W.-Z. Wei, H. Mei, D.-M. Mei, M.-S. Raut, P. Acharya, G.-J. Wang
• Format: Article
• Language: English
• Published: SpringerOpen 2020-10-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-020-08529-z

Abstract For the first time, electrical conduction mechanisms in the disordered material system is experimentally studied for p-type amorphous germanium (a-Ge) used for high-purity Ge detector contacts. The localization length and the hopping parameters in a-Ge are determined using the surface leakage current measured from three high-purity planar Ge detectors. The temperature dependent hopping distance and hopping energy are obtained for a-Ge fabricated as the electrical contact materials for high-purity Ge planar detectors. As a result, we find that the hopping energy in a-Ge increases as temperature increases while the hopping distance in a-Ge decreases as temperature increases. The localization length of a-Ge is on the order of $$2.13^{-0.05}_{+0.07}\mathrm{{A}}^\circ $$ 2 . 13 + 0.07 - 0.05 A ∘ to $$5.07^{-0.83}_{+2.58}\mathrm{{A}}^\circ $$ 5 . 07 + 2.58 - 0.83 A ∘ , depending on the density of states near the Fermi energy level within bandgap. Using these parameters, we predict that the surface leakage current from a Ge detector with a-Ge contacts can be much smaller than one yocto amp (yA) at helium temperature, suitable for rare-event physics searches.