What is Diffusion Voltage in Semiconductor Heterojunctions?

[Aliasa]

I was reading this paper on rectifying properties of mangese oxide films, and came across this mention of diffusion voltage. Can anyone explain please what it is? Here's the context:

In this piece of work, we successfully constructed heterojunctions by growing a manganite $La_{0.9}Hf_{0.1}MnO_{3}$ LHMO on a 0.7 wt % Nd-doped SrTiO$_3$ STON crystal. The heterojunction showed an excellent rectifying property in a wide temperature range from 20 to 300 K. The diffusion voltage $V_d$ and junction resistance $R_jun$ as functions of temperature were studied. The results were discussed by considering the band diagram of LHMO/STON junction and the tunneling current through the junction.​

 

[Greg Bernhardt]

Diffusion voltage is the voltage that is applied to the diffusion layer of a semiconductor. A diffusion layer is the layer of semiconductor material that contains the dopants. A diffusion layer is typically created by diffusion of dopants into the semiconductor material. The diffusion voltage is typically greater than or equal to about 1.5 volts. The diffusion voltage is typically less than or equal to about 10 volts. The diffusion voltage is typically less than or equal to about 3 volts. The diffusion voltage is typically less than or equal to about 2 volts. The diffusion voltage is typically less than or equal to about 1.5 volts.