Click here for input/output files and main program source code for Example 1
This example illustrates a band bending computation for a pn junction in GaAs, as viewed in cross-section with the junction directly below the probe tip. Region 1 is defined as the n-type region, extending over x<=0, and region 2 is the p-type region extending over x>0. The spatial extent of the regions are defined in the routine IGETREG, located in the same file as the Mult3.f main program:
INTEGER FUNCTION IGETREG(X,Y,S)
C
IGETREG=1
IF (X.GT.0.) IGETREG=2
RETURN
END
with the parameters defining the regions given in the FORT.9 input file.
The zero in electrostatic potential is taken by the program to be the region 1 material. The sample voltage as specified in the FORT.9 input file is 0 V, with a contact potential of 0 eV. This problem has a mirror plane lying along the x-axis, so line 46 in the FORT.9 file is set to 1 thus including that mirror plane in the computation.
Output to FORT.11 and FORT.12 gives the electrostatic potential energy (column 2) vs. the z-distance through the vacuum and semiconductor (column 1, in FORT.11) or the radial distance along the surface (column 1, FORT.12). The latter cut is taken at a user-specified angle of 0 degrees relative to the x-direction, with the cut actually corresponds to the closest available angle to that which is 2.8 degrees relative to the x-direction (as listed near the bottom of the FORT.16 output file). When plotted, these potentials appear as: