Surface Morphologies and Optical Properties of Si Doped InGaN Multi-Quantum-Well Grown on Vicinal Bulk GaN(0001) Substrates

Abstract

Morphological and optical properties of Si doped In0.07Ga0.93N multi-quantum-well (MQW) were studied on a vicinal bulk GaN(0001) substrate with low dislocation density. Surface morphology of InGaN MQW was sensitive to the misorientation direction due to the anisotropic step edge structure peculiar to a hexagonal crystal. Appropriate Si doping was useful to suppress instability of the step front and a well-aligned straight step structure was demonstrated for the misorientation direction of [11̄00] with Si doping of 5×1018 cm-3. Low temperature photoluminescence (PL) indicated that good luminescence properties were maintained under the wide range of doping concentration, while PL degradation was observed for heavily doped MQW's. The luminescence properties were discussed based on a self-consistent calculation of the electronic structure of Si-doped MQW's.

InGaN/GaN Structures: Effect of the Quantum Well Number on the Cathodoluminescent Properties

“…Several explanations for PL improvement with increased number of QWs have been suggested such as gradual relaxation in QW region and consequently decreased strain in upper QWs, [12,13] improved crystallographic quality for structures with higher number of QWs in upper part of the active region, [14,15] screening of internal electric field caused by Si doped layer [9] or improved interface roughness caused by Si during the growth of first QW layers. [16] Another possible explanation is suppression of thermionic emission and recapture of carriers in structures with higher number of QWs which was also supported by theoretical model. [17] Based on our AFM results, we suggest an alternative explanation, which takes into account the different size of V-pits in the structures with different numbers of QWs, as seen in Figure 6.…”

Impacts of Si-doping on vacancy complex formation and their influences on deep ultraviolet luminescence dynamics in AlxGa1−xN films and multiple quantum wells grown by metalorganic vapor phase epitaxy

“…int NBE One of the practical ways to obtain better h int NBE by MOVPE of InGaN multiple quantum wells (MQWs) is doping Si in the "barriers." 28,32,33,85) Whilst, appropriate-quantity light doping of Si at around ~´-3 4 10 cm 17 3 during MOVPE of Al 0.6 Ga 0.4 N films 86) and "well layers" of Al 0.68 Ga 0.32 N/Al 0.77 Ga 0.23 N MQWs 87) increased the NBE emission intensities, although Sidoping generally raises E F and decreases E Form of acceptor-type point-defects. [57][58][59][64][65][66] To explain these ameliorative Si-doping effects in the wells or barriers, plenty of models have been proposed.…”

“…[24][25][26][27][28] Accordingly, Si-doping in QWs has been examined extensively. 28,32,33) For increasing t , MGR the concentration of MGRCs (N MGRC ) must be decreased. For this purpose, their exact origins must be identified.…”

“…They are Coulomb screening of F pol , 27,28,88) interface flattening realized by establishing wetting conditions provided by Si, 32,[89][90][91] and the change in the band profiles that gives rise to the proper distribution of electron and hole wavefunctions (Y e and Y , h respectively) in the MQWs. 33,92) Particularly for the above-mentioned Al 0.6 Ga 0.4 N/Al 0.75 Ga 0.25 N MQWs, 87,90) Murotani et al 93) have collected important information written in previous literatures, 86,89,90,94) and thought about the reason for the improved NBE PL efficiency of the proper-amount Si-doped wells, as follows. Because (i) Lebedev et al 89) and Li et al 90) have observed progressively planarized AlGaN surface by Si-doping, (ii) Shimahara et al 86) have shown a remarkable improvement in the NBE luminescence intensity of MOVPE Al 0.6 Ga 0.4 N films by doping Si up to [Si] ≅ 2 × 10 17 cm −3 , and (iii) Uedono et al 94) have reported that [V III ] in the same A l0.6 Ga 0.4 N films was decreased by doping with Si up to 2 × 10 17 cm −3 , Murotani et al 93) thought that Si-doping gave rise to improved interface quality and reduced concentration of NRCs (N NRC ).…”

Imaging Localized Energy States in Silicon-Doped InGaN Nanowires Using 4D Electron Microscopy

“…Several approaches have been developed to manipulate charge carrier dynamics in order to enhance the device functionality of photoactive materials; doping is one of the most effective ways among them. − In general, insertion of impurity species leads to the formation of additional levels in the bandgap of the host material that not only provide additional relaxation routes for the charge carriers, but may also alter the density of states and the band structure, resulting in significant changes in both the optical and electronic properties of the host material. For example, group III nitride semiconductors, in particular, ternary InGaN nanowires (NWs), have gained much attention because of their widespread application as building blocks for diverse optoelectronic and photoelectrochemical devices, − ,− stemming from their photostability and widely tunable direct bandgap from UV to near-IR regions (3.4–0.7 eV), along with the suitability of the NW geometry to allow strain-relaxed growth of complex heterostructures. − To further enhance the efficiencies of InGaN-based devices, Si has been introduced as an n-dopant because it is reported to affect the growth process of NWs, leading to a reduction in structural defects, improvement in their morphology and interface quality, as well as an increase in their thermal stability. , Importantly, Si doping can tune the charge carrier dynamics by altering the band structure and carrier recombination. ,, Moreover, Si doping leads to screening of the internal piezoelectric field, which in turn reduces the quantum-confined Stark effect, resulting in a decrease of carrier localization, increased radiative recombination rate and photoluminescence intensity, and a lower threshold power density for obtaining stimulated emission. ,− …”