H. I. Ralph
Philips
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by H. I. Ralph.
Superlattices and Microstructures | 1985
P. Dawson; Geoffrey Duggan; H. I. Ralph; Karl Woodbridge; G.W. 't Hooft
Abstract We have combined measured 5K excitonic absorption peaks with calculations of the confined particle states to determine the band offsets in GaAs(AlGa)As quantum well heterostructures. Our observations are best fitted with a conduction band-valence band split of about 75:25. This contrasts with the currently accepted value of 85:15 and the recently proposed value of 60:40.
Semiconductor Science and Technology | 1987
J W Orton; Paul F. Fewster; J P Gowers; P. Dawson; Karen J. Moore; P J Dobson; C J Curling; C.T. Foxon; Karl Woodbridge; Geoffrey Duggan; H. I. Ralph
Multi-quantum-well (MQW) structures can be regarded as new materials whose properties are determined by the well and barrier thicknesses Lz and LB and the well depth (which is composition dependent). Measurements of Lz, LB and x are reported for 16 MQW samples grown by molecular beam epitaxy in the AlxGa1-xAs system. Results from X-ray diffraction, photoluminescence excitation spectroscopy and transmission electron microscopy are found to compare well with each other and with values predicted from MBE growth conditions.
Superlattices and Microstructures | 1985
P. Dawson; Geoffrey Duggan; H. I. Ralph; Karl Woodbridge
Abstract Measurements are reported of the photoluminescence decay rate from 55 A GaAs(Al0.35Ga0.65)As multiple quantum well samples prepared by molecular beam epitaxy. Results are reported for the temperature range 4–295 K. Additional measurements of the external photoluminescence efficiency of single thin layers of (AlGa)As lead us to conclude that at the higher temperatures the lifetime in the quantum wells is limited by non-radiative recombination at or close to the (AlGa)As barriers. Following studies of the decay at 4 K we offer a possible alternative explanation of the free exciton decay mechanism to that postulated previously.
In: Chadi, JD and Harrison, WA, (eds.) (pp. pp. 551-554). Springer-Verlag: New York, US. (1985) | 1985
P. Dawson; G. Ouggan; H. I. Ralph; Karl Woodbridge
We have studied the photoluminescence decay rate from GaAs-(AlGa)As quantum well (QW) samples grown by molecular beam epitaxy. Measurements are reported for the range 4-295K. Additional measurements on the luminescence efficiency of (AlGa)As single layers leads us to conclude that the room temperature lifetime in the quantum wells is limited by the optical quality of the barrier material. Decay measurements at 4K are given an interpretation different from those previously published.(1,2)
Physical Review B | 1986
P. Dawson; Karen J. Moore; Geoffrey Duggan; H. I. Ralph; C. T. Foxon
Physical Review B | 1983
P. Dawson; Geoffrey Duggan; H. I. Ralph; Karl Woodbridge
Physical Review B | 1985
Geoffrey Duggan; H. I. Ralph; Karen J. Moore
Physical Review B | 1987
Geoffrey Duggan; H. I. Ralph
Physical Review B | 1987
Geoffrey Duggan; H. I. Ralph; P. Dawson; Karen J. Moore; C.T. Foxon; R.J. Nicholas; J. Singleton; D. C. Rogers
In: (Proceedings) Solid State Physics Conference. (1984) | 1984
H. I. Ralph; Karen J. Moore; Geoffrey Duggan; P. Dawson; P. J. Dobson; Karl Woodbridge
