Band anticrossing in GaNxSb1−x

Abstract

Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions from the valence band to E − and E + can be seen with increasing nitrogen incorporation, consistent with theoretical predictions. The GaNSb band structure has been modeled using a five-band k · p Hamiltonian and a band anticrossing fitting has been obtained using a nitrogen level of 0.78 eV above the valence band maximum and a coupling parameter of 2.6 eV. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2349832͔It is well documented that the anion substitution of dilute quantities of nitrogen into III-V semiconductor compounds results in a sharp decrease in the band gap of the material from that of the host compound. A number of explanations have been suggested to describe this band gap reduction, most notably the band anticrossing model ͑BAC͒, calculations based on empirical pseudopotential methods, and interpretations based on the mixing of the ⌫, L, and X character of the conduction band states. The origin of this band gap reduction is the isoelectronic nature of the nitrogen atoms in the host III-V material. Though the nitrogen atom has the same electron valence as the atom it is replacing, its physical properties ͑size, electronegativity, bond length, etc.͒ are significantly different, resulting in a considerable, highly localized perturbation to the electronic potential surrounding the atom.According to the BAC model this localized deformation in potential results in the formation of an energy level extended in k space which may be resonant with the conduction band of the host. The interaction between the host conduction band and resonant nitrogen level results in the formation of two nonparabolic subbands ͑conventionally denoted E − and E + ͒ given by the relationwhere V MN is the matrix element describing the coupling between the host conduction band ͑E M ͒ and the resonant nitrogen level ͑E N ͒ and has the functional form V MN = C MN ͱ x where C MN is the coupling parameter and x is the nitrogen concentration. 2Nitrogen induced band gap reduction has been observed in many alloys including GaNP, 3 GaNAs, 4 InNAs, 5 and most recently GaNSb. 6 The addition of antimony to the dilute nitride GaNAs has been shown to improve the optical and electronic properties of the material 7 and has been suggested as a possible material for long wavelength optoelectronic devices lattice matched to GaAs. 8 To determine the dependence of the band gap of such materials as a function of nitrogen incorporation, the BAC parameters of the constituent endpoint ternaries must be known. Though these have been well investigated in GaNAs a lack of data is found for GaNSb, a fact highlighted in Vurgaftman and Meyer's review on nitrogen containing III-V materials. 9In this letter, Fourier transform infrared ͑FTIR͒ absorption measurements of GaNSb samples with nitrogen incorporations between 0.2% and 1.0% are presented and preliminary values f...

Highly mismatched GaN1−xSbxalloys: synthesis, structure and electronic properties

“…Such large band gap bowing has also been explained using the BAC model taking into account the modification of the conduction band of GaSb by the localized N states [87,88,90]. Using Fourier transform IR absorption measurements on GaNSb HMAs with N content in the range of 0.2 to 1.0%, Jefferson et al demonstrated that the anticrossing coupling parameter was 2.6 eV with the N state at 0.78 eV above the valence band of GaSb [88].…”

“…4.1 GaSb-rich dilute nitride HMA It was recognized that addition of N to GaSb could potentially produce a direct bandgap material suitable for long-wave infrared detection [84,85,86,87,88,89,90]. By also alloying on the group III site with In, it could be possible to drastically reduce the bandgap while staying lattice matched to a GaSb substrate [89,86,90,91,92].…”

“…Figure 19(a) shows the band structure of a GaN0.82Sb0.18 alloy calculated using our modified BAC model. Here ESb is at 1.2 eV above the VBE of GaN, EN at 0.45 eV above the CBE of GaSb; a coupling parameter of 2.7 eV for the N localized level with the conduction band of GaSb and 2.5 eV for the Sb level with the valence band of GaN were used [88,70]. Since the p-like states of elemental Sb have a relatively large spin-orbit splitting energy of 0.75 eV [103,104] the optical transitions from this band is considered as well.…”

Increased p-type conductivity in GaNxSb1−x, experimental and theoretical aspects

“…[1][2][3][4][5][6][7][8][9][10][11][12] The strong modification of the conduction band when dilute amounts of the host anion of the compound semiconductor is replaced is thought to be caused by N-induced states lying near to the conduction band minimum. [13][14][15][16][17][18][19][20][21] For the alloy GaN x Sb 1Àx , the band gap red shift is especially large. A 300 meV reduction was reported 1,[21][22][23] when incorporating 1% N into GaSb compared to the significantly smaller band gap reduction of 180 meV/% N for GaN x As 1Àx .…”

“…[13][14][15][16][17][18][19][20][21] For the alloy GaN x Sb 1Àx , the band gap red shift is especially large. A 300 meV reduction was reported 1,[21][22][23] when incorporating 1% N into GaSb compared to the significantly smaller band gap reduction of 180 meV/% N for GaN x As 1Àx . 10 The 2-5 lm spectral range of the ternary alloy makes GaN x Sb 1Àx a suitable candidate for mid-infrared applications.…”