Energy band engineering for photoelectrochemical etching of GaN/InGaN heterostructures

Ramesh, Prashanth; Krishnamoorthy, Sriram; Rajan, Siddharth; Washington, Gregory

doi:10.1063/1.4883890

Cited by 9 publications

(7 citation statements)

References 14 publications

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“…Recently, photo-electrochemical (PEC) etching has attracted considerable attention as a bandgap-selective etching technique for separating III-V nitrides heterostructures with different compositions. [20][21][22] By selecting the wavelength of illumination that only generates electron-hole pairs in the narrower-bandgap III-V nitride, the photo-generated electrons transport to an external cathode and photo-generated holes participate in an oxidation reaction and initiate the etching of the narrower-bandgap III-V nitride. Since the ultrafast laser causes phase separation in the damage layer and changes the bandgap energy of the damage layer, the bandgap-selective PEC etching opens a pathway to exfoliate ultrafast laser-processed 4H-SiC wafers without introducing external stress, and fully explore the potential of ultrafast laser slicing of 4H-SiC wafers.…”

Section: Introductionmentioning

confidence: 99%

Slicing of 4H‐SiC Wafers Combining Ultrafast Laser Irradiation and Bandgap‐Selective Photo‐Electrochemical Exfoliation

Shao

Pei

et al. 2023

Adv Materials Inter

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High‐efficiency and low‐loss processing is the mainstay to reduce the cost and deepen the application of 4H silicon carbide (4H‐SiC) wafers in high‐power and high‐frequency electronics. In this study, the high‐yield slicing of 4H‐SiC wafers is realized by combining femtosecond laser irradiation and bandgap‐selective photo‐electrochemical (PEC) exfoliation. By combining light‐absorption measurements, micro‐Raman, and micro‐photoluminescence characterizations, it is found that the damage layer formed inside 4H‐SiC after femtosecond‐laser irradiation consists of amorphous silicon and amorphous carbon. This indicates that the femtosecond‐laser irradiation leads to phase separation in 4H‐SiC. The bandgap of the damage layer is 0.4 eV. Taking advantage of the different bandgap energies of the damage layer and the perfect 4H‐SiC region, the damage layer is removed from the perfect region of 4H‐SiC by using bandgap‐selective PEC etching. During the PEC etching, light‐generated holes can selectively oxidize and corrode the damaged layer with the assistance of the HF solution, and leave the upper and lower perfect 4H‐SiC layers being intact. The current work contributes to the development of the high‐yield and high‐throughput femtosecond laser slicing of 4H‐SiC wafers.

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Section: Introductionmentioning

confidence: 99%

Slicing of 4H‐SiC Wafers Combining Ultrafast Laser Irradiation and Bandgap‐Selective Photo‐Electrochemical Exfoliation

Shao

Pei

et al. 2023

Adv Materials Inter

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“…WGMs have been observed in III-nitride micro-LEDs which are arrays of microdisks fabricated on LED epi-structures grown on sapphire substrates, although lasing could not be achieved due to severe optical leakage through the transparent substrate [27]. Two major schemes have initially been developed to form undercuts that promote optical confinement: selective photoelectrochemical (PEC) etching of sacrificial layers within the epi-structure and selective etching of GaN-on-Si structures [28][29][30]. The PEC etching method has been demonstrated as a way to form undercuts that are needed for optical confinement due to the large refractive index between III-nitride materials and the ambient [31].…”

Section: Introductionmentioning

confidence: 99%

“…The PEC etching method has been demonstrated as a way to form undercuts that are needed for optical confinement due to the large refractive index between III-nitride materials and the ambient [31]. The undercuts are formed by selective PEC etching of a InGaN/InGaN superlattice inserted between the active region and the substrate [29]. Continuous-wave optically-pumped lasing at λ ∼ 428 nm was demonstrated with a threshold of ∼300 W cm −2 and quality factor (Q) of ∼3700 [32].…”

Section: Introductionmentioning

confidence: 99%

Comparison of lasing characteristics of GaN microdisks with different structures

Zi¹,

Fu²,

Cheung³

et al. 2022

J. Phys. D: Appl. Phys.

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The lasing characteristics of optically-pumped GaN microdisks of different configurations, including microdisks with undercuts, microdisks with cladding layers and thin-film microdisks are investigated in this paper. The microdisks, fabricated from a range of epitaxial structures containing blue-light emitting InGaN/GaN multi-quantum wells grown on Si, sapphire or GaN substrates, undergo different processes to form 8µm whispering-gallery mode (WGM) microdisks with different degrees of optical confinement. The microdisks have lasing thresholds ranging from 2.1 to 8.3 mJ/cm2 and quality factors of 1400 to 4200. The lasing characteristics are correlated to the material qualities, optical confinement as well as the overlap of the mode with the MQWs in the microdisk structures. The undercut microdisks benefit from high optical confinement factors but poor overlap factor, while the thin film structures have high overlap factors but low confinement due to absorption by the metallic bonding layers. The findings provide useful insight on ways to optimize GaN microdisk for improving lasing performances.

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“…Since then, extensive work has been carried out on improving surface roughness to overcome these issues. Successful development of photoelectrochemical (PEC) etching gave smooth surfaces and undercut structures by selectively removing sacrificial layers in a heterostructure , which greatly improves the optical confinement of microdisk cavities . Shortly thereafter, continuous‐wave blue lasing at room temperature is demonstrated from GaN microdisks containing InGaN QWs .…”

Section: Introductionmentioning

confidence: 99%

Advances in III‐nitride semiconductor microdisk lasers

Zhang

et al. 2015

Physica Status Solidi (a)

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This paper reviews the recent progress in the design and fabrication strategies of III-nitride semiconductor microdisk lasers on sapphire or Si substrates. Involving more accurate lithography methods in the fabrication boosts quality factors (Q-factors) due to the improved optical confinement of whispering-gallery modes (WGMs) at the rim of the microdisks with smooth sidewalls and perfect circularity. Quantum dots (QDs) as gain medium within the microdisks are investigated and promising for the demonstration of microlasers with super-high Q-factors and ultra-low thresholds. And these QD-cavity systems are also facilitating the research of cavity quantum electrodynamics (QED) in the strong coupling regime and cavity-enhanced single photon emission (SPE) for quantum computing. In this paper, we also report successful fabrication of transferred GaN free-standing microdisks with InGaN quantum wells (QWs) on conductive substrates, which achieves a significant step forward to realize electrically pumped high-quality microdisk lasers on target substrates. Strategies of applying flexible transparent electrodes such as graphene and metallic nanowires are potential effective solutions for realizing current-injection of nitride-based microdisks.ß 2015 WILEYÀVCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Over past few decades, group IIInitride compound semiconductors have been extensively studied and have emerged as indispensable materials for a wide range of optoelectronic devices. With a wide and direct energy bandgap, emissions from III-nitride semiconductors can cover the wavelength range from deep ultraviolet to the near-infrared, making them ideal candidates for incoherent and coherent light sources [1][2][3][4]. Moreover, as epitaxial growth techniques of III-nitride materials become mature, high quality quantum structures such as quantum wells (QWs) and quantum dots (QDs) can be readily achieved, greatly improving the emission efficiency via quantum confinement of the carriers within a small active region so that the possibility of radiative recombination increases, serving as gain medium for highly efficient light emitters [5][6][7]. In addition, the high binding energies of excitons in these wide bandgap materials motivate the research on photon-exciton (or polariton) dynamics and its coherent state polariton lasing in microcavities [8][9][10][11]. In fact, the research of nitride-based microcavity lasers has attracted much attention in past decades for both physical insight of lasing mechanisms in both the weak and strong coupling regimes and their widespread applications [12]. Until now,

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Energy band engineering for photoelectrochemical etching of GaN/InGaN heterostructures

Cited by 9 publications

References 14 publications

Slicing of 4H‐SiC Wafers Combining Ultrafast Laser Irradiation and Bandgap‐Selective Photo‐Electrochemical Exfoliation

Slicing of 4H‐SiC Wafers Combining Ultrafast Laser Irradiation and Bandgap‐Selective Photo‐Electrochemical Exfoliation

Comparison of lasing characteristics of GaN microdisks with different structures

Advances in III‐nitride semiconductor microdisk lasers

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