A critical appraisal of the design, fabrication and assessment of photonic structures in III-V semiconductors

Photonic structures are artificial materials whose dielectric constant is periodically-modulated in one, two or three dimensions. In a manner analogous to the creation of electronic bands, electromagnetic waves propagating in the structure are organized into photonic bands, which are separated by bandgaps where propagating states are forbidden. Spontaneous emission is suppressed for photons inside the photonic bandgap, offering novel approaches to creating high-efficiency light-emitting structures. The objective of this thesis is to assess a broad range of issues concerning the use of photonic structures in light-emitting devices based on GaAs. A comprehensive review was undertaken to identify the most suitable techniques for modelling, fabrication and experimental assessment of photonic structures in this context. The key results are: (1) The most appropriate method for calculating photonic band structure is the plane wave method, which was used with real-world values for the dielectric constant to identify appropriate dimensions for prototype structures. However the transfer matrix method is better for calculating the transmission and reflection coefficients, which are quantities that can be compared directly with experimental results. Software was written to extend this method to structures with hexagonal symmetry. (2) Electron beam lithography and electron cyclotron plasma etching were used to fabricate two-dimensional photonic structures in GaAs-based materials. Highly-uniform structures were produced over areas up to 200 #mu#m"2, and with feature sizes down to 50nm. This etching technique, which uses low energy ions, is particularly suited to device processing because it causes less etch damage. Other structures reported in the literature have used high-energy etch processes. (3) An experimental setup was developed to measure the transmission and reflection through a photonic structure etched into a waveguide. The technique, which uses a broadband light source to provide a wide spectral range, should allow the observation of both band edges on the same sample - this has not been achieved in any reported measurements. (author)Available from British Library Document Supply Centre-DSC:D206606 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo