Donors in silicon is a potential scalable qubit platform for quantum technologies due the compatibility with existing microelectronic fabrication. Bismuth donors are particularly interesting due to their large nuclear spin and strong hyperfine coupling, manifesting as a 20-dimensional Hilbert space with a hyperfine splitting of 30.5 µeV which can be resolved without the application of a magnetic field. Fully scalable manufacturing of deterministically positioned donors can only be achieved through single ion implantation. Here we will present a review of our recent optical characterisation studies of implanted Bi donors which address the challenges of by the implantation route for the delivery of usable materials for quantum technologies.
The strain-induced wafer bow for VCSEL epitaxial structures grown on GaAs substrates is measured and compared to that of Ge substrates. We find that the ~ 160 μm height difference between the centre and edge of a GaAs wafer results in a significant temperature gradient and hence has a large effect on oxidation rate in the high-Al layer in the top DBR of the epi-structure. We measure a resultant centre-to-edge variation in oxidation length of ~ 3 μm for a GaAs wafer. We assess the contributions of wafer bow and epi-layer non-uniformity, as well as temperature variation in the furnace, and find that the effect of the bow dominates.
We employ a Very Quick Fabrication (VQF) method to rapidly produce oxide confined VCSELs across a 150 mm GaAs substrate wafer to assess the impact on device performance. By measuring threshold current density between 20 and 70 ℃, we find ~ 25 ℃ variation in the temperature corresponding to the alignment of the spectral peak of gain with the cavity resonance wavelength. However, we still find that the threshold current density at zero detuning, is lower for edge devices, which we attribute to material variation.
We disentangle the different contributions to device performance to isolate the effect of material variation. We compare this remaining spatial non-uniformity to that of VCSELs grown on Ge substrates.
A simplified fabrication process for VCSELs which employs oxidation-vias for definition of the laser aperture and bond pad is applied to a full 150mm wafer as a technique for material characterisation. This Quick Fabrication process produces representative VCSELs, with performance comparable to standard process VCSELs, with threshold currents for 8μm oxide-aperture devices measured between 0.8 and 1.3mA for both device types. The redshift of the lasing wavelength and threshold currents are used for rapid assessment of the VCSEL wafers.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.