Lithium-free segmentable hyperpure germanium detector via Pulsed Laser Melting

High-purity germanium (HPGe) γ-ray detectors require thin segmentable n+ contacts that remain stable during annealing for radiation-damage recovery [1,2]. Li-diffused contacts introduce dead layers of millimetric scale, limit segmentation, and are unstable during typical recovery treatments (~378 K for tens of hours). We present a lithium-free junction technology based on a Sb precursor deposited by magnetron sputtering followed by pulsed laser melting (PLM) diffusion treatment. PLM melts only a shallow Ge surface layer and incorporates dopants during rapid epitaxial regrowth, yielding an abrupt, ultra-thin n+ junction, while preserving the hyperpure bulk and enabling photolithographic segmentation. We fabricated a 35×35 mm², 1.6 mm-thick planar detector with six strips plus a guard ring. 241Am and 133Ba spectroscopy showed standard-like photopeak resolution on multiple segments, while 60Co transient signals demonstrated position sensitivity suitable for pulseshape analysis. The segmented PLM junction remained stable after an annealing cycle representative of neutron-damage recovery [3]. Finally, the process was then scaled to 1-2 cm-thick crystals, refining contamination control, cleaning, gold-free photolithography, and mechanical chemical polishing. Reducing contactinduced stress and adding a thick Al layer raised the breakdown voltage above the depletion voltage, enabling thick, segmented, lithium-free HPGe detectors [1,2,3]. [1] S. Bertoldo et al. EPJA 2021, 57, 177. [2] J. Eberth et al. EPJA 2023, 59, 179. [3] S. Bertoldo et al. Mat. Sci. Semiconductor Processing, 2025, 200, 109967.