Deep-UV optical gain in AlGaN-based graded-index separate confinement heterostructure

Abstract

We propose AlGaN-based GRaded-INdex Separate Confinement Heterostructure as a candidate for electrically pumped deep-UV semiconductor laser. Strong compositional fluctuations were introduced in the active region (75 nm-thick Al 0.72 Ga 0.28 N film grown by RF Plasmaassisted Molecular Beam Epitaxy) to obtain net modal optical gain peaked at 257 nm in excess of 80 cm −1 . We measured an optical gain threshold of 14 µJ/cm 2 . Because of polarization-doping of the compositionally graded AlGaN regions, which automatically leads to the formation of p-i-n junction, these results pave the way for lasing under electrical injection.

Ultraviolet optoelectronic devices based on AIGaN alloys grown by molecular beam epitaxy

“…[129,[134][135][136] Such laser device structures were successfully used in traditional III-V compounds and were found to have the lowest threshold current. Besides the efficient carrier and optical field confinement in lasers based on the GRINSCH configuration, such laser designs based on AlGaN alloys have the additional advantage of automatically leading to a p-n junction formation, [134] owing to opposite compositional grading of the AlGaN alloys in either side of the active region of the device.…”

“…Stimulated emission and optical gain in these devices was also demonstrated. [136] The crystal microstructure and optical properties of such GRINSCH devices can be found in the original papers. [129,[134][135][136] …”

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

“…As members of the III-nitrides family, AlxGa1-xN alloys have become a key material for deep ultraviolet (DUV) optoelectronic devices [1][2][3][4][5]. Even though bulk AlN substrates have been developed and are suitable for device applications, they are still expensive and only available in small sizes.…”

Effect of indium in Al0.65Ga0.35N/Al0.8Ga0.2N MQWs for the development of deep‐UV laser structures in the form of graded‐index separate confinement heterostructure (GRINSCH)

“…To address the issues of poor doping of such alloys, as well as to increase the confinement factor of the optical mode in deep UV lasers we have recently proposed the growth of these devices in the form of graded‐index‐separate‐confinement‐heterostructure (GRINSCH) . In such a structure, the compositionally graded regions of AlGaN in either side of the active region are doped by polarization n‐ and p‐type, respectively , while simultaneously they increase the confinement of the optical mode due to variation of the index of refraction of the compositionally graded AlGaN films …”

“…To address the issues of poor doping of such alloys, as well as to increase the confinement factor of the optical mode in deep UV lasers we have recently proposed the growth of these devices in the form of graded-indexseparate-confinement-heterostructure (GRINSCH) [34]. In such a structure, the compositionally graded regions of AlGaN in either side of the active region are doped by polarization n-and p-type, respectively [35], while simultaneously they increase the confinement of the optical mode due to variation of the index of refraction of the compositionally graded AlGaN films [34,[36][37][38][39] In this paper, we compare the growth, the crystal structure, and the optical properties of two deep-UVemitting AlGaN-based GRINCH structures, grown by plasma-assisted MBE. In the first structure the active region, consisting of AlGaN QWs, was grown under excess Ga than required for stoichiometric growth.…”