Alexandre W. Walker
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Quasi-open circuit response times of single- and multi-junction InGaAs photonic power converters Open
Photonic power converters provide an emerging alternative to traditional metallic cabling due to their immunity to electromagnetic interference and for minimizing fire hazards as well as their ability to wirelessly power loads. In this wor…
Machine learning enhanced design and knowledge discovery for multi-junction photonic power converters Open
Machine learning is proving to be a revolutionary tool across many disciplines, including optoelectronic device design. In this report, we compare classical and machine learning enhanced design optimization methodologies. We investigate, a…
Multi-junction laser power converters exceeding 50% efficiency in the short wavelength infrared Open
Photonic or laser power converters are crucial components in power-by-light systems. However, their use in long-distance applications has been hindered by low efficiencies and output voltages within the optical fiber transmission window of…
Extended Temperature Modeling of InGaAs/InP SPADs Open
We present a simulation method to estimate the dark count rate (DCR), photon detection probability (PDP), and dark current of InGaAs/InP single-photon avalanche diodes (SPADs) from 225K to 300K. All simulations are performed completely in …
Zn diffusion depth effect on photoresponse uniformity in InP/InGaAs avalanche photodiodes Open
Numerical simulation of the electric field distribution and photocurrent response of a planar InP/InGaAs avalanche photodiode is presented for small variations of the multiplication width. The Zn dopant diffusion front is obtained by numer…
Guard-Ring-Free InGaAs/InP Single-Photon Avalanche Diode Based on a Novel One-Step Zn-Diffusion Technique Open
This work presents a novel InGaAs/InP SPAD structure fabricated using a selective area growth (SAG) method. The surface topography of the selectively grown film deposited within the 70 mu m diffusion apertures is used to engineer the Zn di…
Carrier recombination dynamics in Ga <sub>0.51</sub> In <sub>0.49</sub> P double-heterostructures up to 500 K Open
The bulk minority carrier lifetime and interface recombination velocity (IRV) in GaInP double-heterostructures (DHs) lattice matched to GaAs are extracted using time-resolved photoluminescence (PL) measured between 300 and 500 K. Effective…
Measurement of the non-radiative minority recombination lifetime and the effective radiative recombination coefficient in GaAs Open
The combination of time-resolved (TR) and power-dependent relative (PDR) photoluminescence (PL) measurements reveals the possibility of separating the radiative and non-radiative minority carrier lifetimes and measuring the sample-dependen…
Extracting Nonradiative Parameters in III–V Semiconductors Using Double Heterostructures on Active p-n Junctions Open
A novel method of extracting the nonradiative lifetime of Ga0.51In0.49P lattice matched to GaAs by exploiting luminescence coupling is discussed. The method requires a GaInP double heterostructure monolithically grown on a GaAs photodetect…
Minority carrier diffusion length, lifetime and mobility in p-type GaAs and GaInAs Open
Minority carrier diffusion lengths and lifetimes were determined for p-type Ga(1-x)InxAs with an In-content of 0 ≤ x ≤ 0.53 by cathodoluminescence and time-resolved photoluminescence measurements respectively under low injection conditions…
Minority carrier diffusion lengths and mobilities in low-doped n-InGaAs\n for focal plane array applications Open
The hole diffusion length in n-InGaAs is extracted for two samples of\ndifferent doping concentrations using a set of long and thin diffused junction\ndiodes separated by various distances on the order of the diffusion length. The\nmethodo…
Procedure to decouple reflectance and down-shifting effects in luminescent down-shifting enhanced photovoltaics Open
The down-shifting (DS) process is a purely optical approach used to improve the short-wavelength response of a solar cell by shifting high-energy photons to the visible range, which can be more efficiently absorbed by the solar cell. In ad…
Minority carrier diffusion lengths and mobilities in low-doped n-InGaAs for focal plane array applications Open
The hole diffusion length in n-InGaAs is extracted for two samples of different doping concentrations using a set of long and thin diffused junction diodes separated by various distances on the order of the diffusion length. The methodolog…
View article: Status of Four-Junction Cell Development at Fraunhofer ISE
Status of Four-Junction Cell Development at Fraunhofer ISE Open
\nFour-junction solar cells are being developed for space applications as they promise higher efficiencies compared to the present GaInP/GaInAs/Ge triple-junction industry standard. There are multiple technological routes to achieve four-j…
Nonradiative lifetime extraction using power-dependent relative photoluminescence of III-V semiconductor double-heterostructures Open
A power-dependent relative photoluminescence measurement method is developed for double-heterostructures composed of III-V semiconductors. Analyzing the data yields insight into the radiative efficiency of the absorbing layer as a function…
Influence of a Very Efficient Back Reflectors on the Quantum Efficiency of Solar Cells Open
Very reflective back side reflectors directly below the active region of a solar cell alter the photon absorption and carrier collection dynamics in a manner that can be exploited for enhanced efficiency. The enlarged optical path increase…