为了进一步了解在金属,半导体接触势垒高度计算中采用半导体平均键能Em作为参考能级的合理性,本文在金属-半导体超晶格的LMTO—ASA能带计算中,引用“冻结势”方法,计算了(Ge2)4(2Al)6(001),(Ge2)4(2Au)6(001),(Ge2)4(2Ag)6(001),(GaAs)4(2Al)6(001),(GaAs)4(2Au)6(001)和(GaAs)4(2Ag)6(001)等超晶格金属-半导体界面两侧的金属费米能级EF(M)和半导体平均键能Em(S),研究发现,在超晶格的金属-半导体界面两侧,金属的费米能级EF(M)与半导体的平均键能Em(S)几乎处于同一能量水平线上,Em(S)≈EF(M),也就是EF(M)与Em(S)在界面两侧相互“对齐”,因此,在理想金属,半导体接触的势垒高度理论计算中,采用半导体平均键能Em作为参考能级,可以获得比较可靠的计算结果。
To further understand the average-bond-energy Em ,which can be taken as the reference energy level in the calculation of metal-semiconductor contacts, the Em of the semiconductor and the Fermi level EF (M) of the metal on both sides of the metal-semiconductor inte rface in ( Ge2 ) 4 ( 2Al ) 6 ( 001 ), ( Ge2 ) 4 (2Au) 6 ( 001 ), ( Ge2 ) 4 ( 2 Ag ) 6( 001 ), ( GaAs ) 4 ( 2Al ) 6 ( 001 ), (GaAs)4 (2Au)6 (001),and (GaAs)4(2Ag)6(001) superlattices are investigated by the calculation of the LMTO-ASA energy band structure with the frozen-potential method. The results show that Em of the semiconductor and EF (M) of the metal are almost on the same horizontal energy level, i. e. Em ≈ EF (M). In other words, Em and EF (M) on both sides of the metal-semiconductor interface are mutually aligned. This indicates that reliable calculation results can be obtained by taking Em as the reference energy level in the calculation of the barrier height of ideal metal-semiconductor contacts.