The utilization of electron beam lithography (EBL) as a wafer scale technique for the fabrication of compound semiconductor devices provides unique challenges in terms of both application and throughput. We report on wafer scale EBL in the context of fabricating edge emitting lasers on 150 mm indium phosphide (InP) substrates. A hybrid electro-optical lithography process is used to pattern typical ridge waveguide (RWG) laser structures, while overcoming some of the practical challenges associated with fabricating these devices on large wafer platforms. This technique is demonstrated to reduce patterning times by up to a factor of 20 compared to conventional EBL processes. Moreover, we motivate the application of hybrid lithography by considering the loading effect of etching 150 mm InP wafers and the benefit of transitioning to a ‘low open area’ mask geometry.

We have developed a process to mass-produce quantum dot micropillar cavities using direct-write lithography. This technique allows us to achieve mass patterning of high-aspect ratio pillars with vertical, smooth sidewalls maintaining a high quality factor for diameters below 2.0 μm. Encapsulating the cavities in a thin layer of oxide (Ta2O5) prevents oxidation in the atmosphere, preserving the optical properties of the cavity over months of ambient exposure. We confirm that single dots in the cavities can be deterministically excited to create high-purity indistinguishable single photons with interference visibility (0.941 ± 0.008).

Development of a quick fabrication (QF) method for commercial wafer characterisation based on rapid feedback of VCSEL performance. We report on the design of the fabrication process including the systematic removal of time-consuming steps of planarization, oxidation and substrate lapping, and the associated impact on device performance and yield. We show comparable performance of the oxide-confined QF etched trench VCSELs and full process devices and we show that unoxidised devices behave as large aperture oxidised devices. Further, we demonstrate similar performance of substrate-lapped and -unlapped VCSELs between 1.0-1.2 Ith with a difference in current tuning typically 0.064nm/mA.

High-volume low-cost production of vertical cavity surface emitting lasers (VCSELs) will allow their exploitation in new commodity markets. We report the successful scaling up from research level fabrication to produce oxide confined VCSELs across a whole 150mm wafer. On-wafer light-current-voltage (L-I-V) and spectral measurements are analyzed to determine the cross-wafer variations in threshold current, threshold current densities and emission wavelength, which is compared with reflectivity measurements taken immediately after growth. We examine the dependence of VCSEL performance on fabrication parameters over a range of device dimensions to assess whether variation arises from non-uniformity of the epitaxial material or wafer processing.

We have developed an inductively coupled plasma etching technique using a Faraday cage to create suspended gallium-nitride devices in a single step. The angle of the Faraday cage, gas mix, and chamber condition define the angle of the etch and the cross-sectional profile, which can feature undercut angles of up to 45°. We fabricate singly- and doubly-clamped cantilevers of a triangular cross section and show that they can support single optical modes in the telecom C-band.