Neutrinoless Double Beta Decay with Germanium Detectors: 1026 yr and Beyond

In the global landscape of neutrinoless double beta ($0\nu\beta\beta$) decay search, use semiconductor germanium detectors provides many advantages. The excellent energy resolution, negligible intrinsic radioactive contamination, possibility enriching crystals up to 88% in $^{76}$Ge isotope as well high detection efficiency, are all key ingredients for highly sensitive $0\nu\beta\beta$ search. MAJORANA and GERDA experiments successfully implemented (Ge) detectors, reaching an resolution $2.53 \pm 0.08$ keV at Q$_{\beta\beta}$ unprecedented low background level $5.2 \times 10^{-4}$ cts/(keV$\cdot$kg$\cdot$yr), respectively. this paper, we will review path search with Ge from original idea E. Fiorini et al. 1967, final recent results experiment setting a limit on half-life $T_{1/2} > 1.8 10^{26}$ yr (90\% C.L.). We then present LEGEND project designed reach sensitivity $10^{28}$ beyond, opening way exploration normal ordering region.