as to provide substantial lattice matching to the lattice structure c the substrate specifically be x zn 1 x te x se 1 x graded gap semiconductor layers are provided for application as ohmic contacts to p type znse zns x se 1 x zn 1 x cd x s zn 1 x cd x s y se 1 y zn 1 x mg x s y se 1 y and other ii vi compound semiconductors used in lasers grown on gaas substrates due to the close lattice match to gaas substrate graded x 1 x contact allow for the entire device structure to be grown within the pseudomorphic limit application_number US 8730793 A description bete znse ohmic contacts were modeled using the material constants listed in the table ______________________________________table of constants znse bete______________________________________bandgap ev 2 67 2 70electron affinity ev 3 82 2 0hole mobility cm sup 2 v s at n sub a 10 sup 18 cm sup 3 20 20electron mass m sub e m sub o 0 17 0 17hole mass m sub h m sub o 65 65acceptor ionization energy mev 100 100low frequency dielectric constant 9 2 9 2______________________________________ in the calculations which follow material constants of be x zn 1 x te x se 1 x were obtained from linear interpolation of the znse and bete parameters listed in the table the 2 0 ev value of electron affinity for bete results from the assumed 1 8 ev in valence band discontinuity of bete znse heterojunction the energy bands and current voltage characteristics were calculated by solving poison 39 s equation with electron and hole continuity equations within one dimensional heterostructures with reference to the drawings fig1 a illustrates an energy band diagram of a staggered p bete p znse.