Exploring time-resolved photoluminescence for nanowires using a three-dimensional computational transient model

Abstract

Time-resolved photoluminescence (TRPL) has been implemented experimentally to measure the carrier lifetime of semiconductors for decades. For the characterization of nanowires, the rich information embedded in TRPL curves has not been fully interpreted and meaningfully mapped to the respective material properties. This is because their three-dimensional (3-D) geometries result in more complicated mechanisms of carrier recombination than those in thin films and analytical solutions cannot be found for those nanostructures. In this work, we extend the intrinsic power of TRPL by developing a full 3-D transient model, which accounts for different material properties and drift-diffusion, to simulate TRPL curves for nanowires. To show the capability of the model, we perform TRPL measurements on a set of GaAs nanowire arrays grown on silicon substrates and then fit the measured data by tuning various material properties, including carrier mobility, Shockley-Read-Hall recombination lifetime, and surface recombination velocity at the GaAs-Si heterointerface. From the resultant TRPL simulations, we numerically identify the lifetime characteristics of those material properties. In addition, we computationally map the spatial and temporal electron distributions in nanowire segments and reveal the underlying carrier dynamics. We believe this study provides a theoretical foundation for interpretation of TRPL measurements to unveil the complex carrier recombination mechanisms in 3-D nanostructured materials.

Room-Temperature Midwavelength Infrared InAsSb Nanowire Photodetector Arrays with Al2O3 Passivation

“…The correlation between the increase of PL emission and the improvement in surface recombination velocity (in units of cm/s) was further studied. Typically, the surface recombination velocity of nanowires is extracted by time-resolved photoluminescence (TRPL), as shown in many pioneering studies. , However, we believe that the rich information inherent in the PL spectra can still be harnessed to unveil the surface dynamics. The basic idea is as follows.…”

“…This is mainly due to the significant nonradiative recombination at the arsenic-rich InAsSb nanowire surfaces, which is well known. Since the performance of nanowire-based devices is predominantly affected by the surface quality due to their large surface-to-volume ratios, 28,29 it is critical to develop a high-quality surface passivation to improve the internal quantum efficiency (IQE) of InAsSb nanowire photodetectors for room-temperature photodetection at MWIR. 8,9 In this work, we demonstrated uncooled InAsSb photodetector arrays on InP substrates for photodetection at MWIR, grown by selective-area metal-organic chemical vapor deposition (SA-MOCVD).…”

Uncooled Photodetector at Short-Wavelength Infrared Using InAs Nanowire Photoabsorbers on InP with p–n Heterojunctions

“…These modifications can be accomplished by developing device schemes based on bottom-up vertical III–V nanowires. The unique properties of nanowires, namely, small junction area and heteroepitaxy, are particularly advantageous in not only achieving a lower dark current density but also preventing threading dislocations (by elastic deformation at the nanowire–substrate heterointerfaces) and minimizing point dislocations, which are undesirable in the traditional epitaxy for bulk structures. , …”

“…Note that the dark current in a three-dimensional (3D) nanowire–substrate p – n diode with a heterointerface is predominantly determined by the heterointerface quality and the nanowire–air (or nanowire-passivation) interface quality around the nanowire depletion region. Therefore, the carrier dynamics in nanowires are more complicated than in bulk devices, , which needs to be thoroughly considered when developing high-performance nanowire-based optoelectronic devices.…”

“…The carrier traps are specified as acceptor-like surface traps (neutral when unoccupied and negatively charged when occupied by electrons). For nanowire–substrate ( n -InAs/ p -InP), nanowire–air ( n -InAs/vacuum), and nanowire–mask ( n -InAs/SiO 2 ) interfaces, we introduce surface recombination velocities instead of trap states to reproduce the nonradiative recombination mechanisms, as shown in previous studies for heterointerfaces . Finally, the simulated dark current of one unit cell is multiplied by 36 000 (the number of unit cells within the 100 μm × 100 μm nanowire array) to find the total dark current produced by the nanowire array.…”