Distributed Bragg reflectors (DBRs) are the key building blocks of various optoelectronic and photonics devices. Broadband DBRs in the visible spectral range using the concept of Anderson localization of light in a disordered system are presented. The results demonstrate a ≈2.5X (from ≈80 to ≈200 nm) enhancement of the stopband width for a random DBR compared with a periodic DBR with the same configuration for both dielectric and nanoporous GaN material systems. The described method is beneficial for various applications, including air‐guiding waveguides and light‐emitting diodes with improved light‐extraction efficiency.
An electrically pumped surface-emitting semiconductor green laser
Surface-emitting semiconductor lasers have been widely used in data communications, sensing, and recently in Face ID and augmented reality glasses. Here, we report the first achievement of an all-epitaxial, distributed Bragg reflector (DBR)–free electrically injected surface-emitting green laser by exploiting the photonic band edge modes formed in dislocation-free gallium nitride nanocrystal arrays, instead of using conventional DBRs. The device operates at ~523 nm and exhibits a threshold current of ~400 A/cm 2 , which is over one order of magnitude lower compared to previously reported blue laser diodes. Our studies open a new paradigm for developing low-threshold surface-emitting laser diodes from the ultraviolet to the deep visible (~200 to 600 nm), wherein the device performance is no longer limited by the lack of high-quality DBRs, large lattice mismatch, and substrate availability.
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- Award ID(s):
- 1709207
- PAR ID:
- 10198296
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2375-2548
- Page Range / eLocation ID:
- eaav7523
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Electrically pumped lasing from hybrid organic–inorganic metal‐halide perovskite semiconductors could lead to nonepitaxial diode lasers that are tunable throughout the visible and near‐infrared spectrum; however, a viable laser diode architecture has not been demonstrated to date. Here, an important step toward this goal is achieved by demonstrating two distinct distributed feedback light‐emitting diode architectures that achieve low threshold, optically pumped lasing. Bottom‐ and top‐emitting perovskite light‐emitting diodes are fabricated on glass and Si substrates, respectively, using a polydimethylsiloxane stamp in the latter case to nanoimprint a second‐order distributed feedback grating directly into the methylammonium lead iodide active layer. The devices exhibit room temperature thresholds as low as ≈6 µJ cm−2, a peak external quantum efficiency of ≈0.1%, and a maximum current density of ≈2 A cm−2that is presently limited by degradation associated with excessive leakage current. In this low current regime, electrical injection does not adversely affect the optical pump threshold, leading to a projected threshold current density of ≈2 kA cm−2. Operation at low temperature can significantly decrease this threshold, but must overcome extrinsic carrier freeze‐out in the doped organic transport layers to maintain a reasonable drive voltage.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.aav7523
