Electrical properties of a metal-germanium-topological insulator (metal/n-Ge/p-Bi₂Te₃) heterostructure devices

This work presents topological insulator (TI) heterojunction Metal/n-Ge/Bi₂Te₃, by growing a thin TI film of Bi₂Te₃ on an n-type Germanium (Ge) substrate. The microstructure and morphology of the developed Bi₂Te₃ film are analyzed. The electrical behavior of the Metal/n-Ge/Bi₂Te₃ heterojunction is examined by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The performance of the heterostructure was examined by depositing different metallic contacts. Metal contacts of aluminum (Al), silver (Ag), and platinum (Pt) were used, and they formed Schottky contact with Ge and an ohmic contact with Bi₂Te₃. Pt/n-Ge/Bi₂Te₃ heterostructure was found best in terms of rectification ratio (RR) = 122.7, the figure of merit (FOM) = 49.5, and ideality factor (n) = 7.33 with small series resistance (R_s). The space-charge limited current (SLSC) and ohmic conduction are the transport mechanisms that govern these heterojunctions at a different voltage, affecting its performance. The influence of n-Ge/p-Bi₂Te₃ junction on the performance of Metal/n-Ge/Bi₂Te₃ is analyzed. The experimental results are fitted by two-diode simulation and current density–voltage (J–V) and local ideality factor—voltage n–V plots of these heterojunctions are studied for the recombination current (J₀₂). This study is significant in terms of the electrical performance of the Ge-TI-based, heterojunction devices.