FABRICATION AND CHARACTERIZATION OF La2-xSrxCuO4/Nb-SrTiO3 HETEROJUNCTIONS IN DIFFERENT DOPED REGIMES

Two types of p–n junction were fabricated by depositing underdoped La 1.9 Sr 0.1 CuO 4 film and overdoped La 1.8 Sr 0.2 CuO 4 film on n -type 0.5 wt.% Nb -doped SrTiO 3 (NSTO) substrates using pulsed laser deposition technique (PLD), respectively. Current–voltage (I–V) characteristics of the La 2-x Sr x CuO 4/NSTO heterojunction were measured in the temperature range from 5 K to 300 K. All I–V curves show a fine rectifying property and a visible reduction of the diffusion potential (Vd) is observed, but the behaviors of Vd are vastly different for the underdoped and overdoped regimes at temperatures below Tc. Analysis results show that the characteristics of the heterojunction are possibly affected not only by the superconducting gap of LSCO at Tc, but also by the depletion layer in the interface of LSCO/NSTO junction. The variation of the depletion layer is possibly different under the same applied bias voltages for the underdoped La 1.9 Sr 0.1 CuO 4/NSTO junction and overdoped La 1.8 Sr 0.2 CuO 4/NSTO junction due to the difference of carrier density at La 1.9 Sr 0.1 CuO 4 and La 1.8 Sr 0.2 CuO 4.