AlGaN/GaN intersubband transitions for Tb/s 1.55-μm optical switches

The feasibility of the inter-subband transition (ISBT) in Al(Ga)N/GaN quantum wells (QWs) as a device mechanism for ultrafast optical switches is theoretically investigated. The 1.55-micrometers ISBT is shown to be feasible because of its large conduction band discontinuity. The inter-subband relaxation time at 1.55 micrometers is estimated to be about 100 fs, which is 20 - 30 times shorter than that in InGaAs QWs. A large electron-electron scattering rate causes a short dephasing time (about 10 fs), which reduces the peak value of the third-order nonlinear susceptibility. At a high carrier density, however, the dephasing time is increased because of the screening and the exclusion, which enhances the nonlinear susceptibility. Ultrafast relaxation of the inter-subband optical nonlinearity in GaN QWs is little affected by the delay in intra-subband energy relaxation caused by non-equilibrium phonons. These characteristics suggest that the ISBT in nitride QWs is a promising mechanism for multi-terabit/s optical switches.

[1]  Ravindra P. Joshi,et al.  Nonequilibrium electron distributions and phonon dynamics in wurtzite GaN , 1996 .

[2]  Michael S. Shur,et al.  Comparison of high field electron transport in GaN and GaAs , 1997 .

[3]  Akio Sasaki,et al.  All‐optical modulation using an n‐doped quantum‐well structure , 1990 .

[4]  Akio Sasaki,et al.  Enhanced interband-resonant light modulation by intersubband-resonant light in selectively n-doped quantum wells , 1995 .

[5]  Erich P. Ippen,et al.  Feasibility of 1.55 µ m Intersubband Photonic Devices Using InGaAs/AlAs Pseudomorphic Quantum Well Structures , 1994 .

[6]  Huang,et al.  Dielectric continuum model and Fröhlich interaction in superlattices. , 1988, Physical review. B, Condensed matter.

[7]  Molinari,et al.  Microscopic calculation of the electron-phonon interaction in quantum wells. , 1992, Physical review. B, Condensed matter.

[8]  John E. Bowers,et al.  Femtosecond studies of carrier dynamics in InGaN , 1997 .

[9]  Clifton G. Fonstad,et al.  Multiband coupling effects on electron quantum well intersubband transitions , 1995 .

[10]  L. Ram-Mohan,et al.  Can normal‐incidence absorption be realized with n‐doped (001)‐grown direct‐gap quantum wells? , 1995 .

[11]  K. Bachem,et al.  Resonant Raman scattering in GaN/(AlGa)N single quantum wells , 1997 .

[12]  S. Hughes,et al.  Ultrafast carrier - carrier scattering in wide-gap GaN semiconductor laser devices , 1997 .

[13]  H. Morkoç,et al.  Direct measurements of electron-longitudinal optical phonon scattering rates in wurtzite GaN , 1997 .

[14]  L. C. West,et al.  First observation of an extremely large‐dipole infrared transition within the conduction band of a GaAs quantum well , 1985 .

[15]  M. E. Flatte,et al.  GENERALIZED SUPERLATTICE K.P THEORY AND INTERSUBBAND OPTICAL TRANSITIONS , 1996 .

[16]  Michael S. Shur,et al.  Elastic strain relaxation and piezoeffect in GaN-AlN, GaN-AlGaN and GaN-InGaN superlattices , 1997 .

[17]  Martin M. Fejer,et al.  Near-infrared wavelength intersubband transitions in high indium content InGaAs/AlAs quantum wells grown on GaAs , 1997 .