Room-temperature continuous-wave operation of GaN-based vertical-cavity surface-emitting lasers fabricated using epitaxial lateral overgrowth

Izumi, Shouichiro; Fuutagawa, Noriyuki; Hamaguchi, Tatsushi; Murayama, Masahiro; Kuramoto, Masaru; Narui, Hironobu

doi:10.7567/apex.8.062702

Cited by 78 publications

(47 citation statements)

References 18 publications

(34 reference statements)

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“…In this study, we investigated the properties of this type of VCSEL in greater detail, such as the reflectance spectra of both DBRs, a cross‐sectional scanning electron microscopy (SEM) analysis of the ELO structure, and the reliability of the ITO contact on p‐type gallium nitride. Furthermore, we studied the effects of increasing the number of quantum wells and of introducing boron implantation, rather than using a SiO 2 layer as in our previous report .…”

Section: Introductionmentioning

confidence: 99%

Milliwatt‐class GaN‐based blue vertical‐cavity surface‐emitting lasers fabricated by epitaxial lateral overgrowth

Hamaguchi¹,

Fuutagawa²,

Izumi³

et al. 2016

Physica Status Solidi (a)

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We have achieved continuous‐wave (CW) operation of gallium nitride (GaN)‐based vertical‐cavity surface‐emitting lasers (VCSELs) fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors (DBRs) as masks for selective growth. The GaN VCSELs exhibited CW operation at a wavelength of 453.9 nm, and the maximum output power was 1.1 mW, which is the highest value reported to date. GaN‐based materials have presented challenges for obtaining DBRs with high reflectivity and a wide stopband, precise control of the cavity length and a lateral confinement structure to provide laser operation. The proposed VCSEL is immune to these concerns. Its two dielectric DBRs were obtained free from cracks. A high reflectance of more than 99.9% and a stopband with a width of 80–97 nm were obtained for both DBRs. The cavity length was controlled by epitaxial growth to as short as 4.5 µm. An ITO contact electrode on p‐type GaN, which is required for a lateral confinement structure, showed electrical reliability under a high current density of 59.6 kA cm−2. The present data demonstrate that the fabrication process adopted here overcomes the shortcomings that have prevented the widespread use of GaN‐based VCSELs.

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Section: Introductionmentioning

confidence: 99%

Milliwatt‐class GaN‐based blue vertical‐cavity surface‐emitting lasers fabricated by epitaxial lateral overgrowth

Hamaguchi¹,

Fuutagawa²,

Izumi³

et al. 2016

Physica Status Solidi (a)

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“…This is typically achieved using a flip-chip design, [23][24][25][26][27][28][29][30][31][32] however it has also been demonstrated recently using lateral epitaxial overgrowth (LAE). 33 The hybrid DBR is advantageous because of the high thermal conductivity of the epitaxial n-DBR layers, which improves heat dissipation from the active region of the device. However, epitaxial III-nitride DBRs are non-trivial to grow, due to the large lattice mismatch leading to cracking, in the case of AlGaN/GaN-based DBRs, 37,41,42 and the general complications involved in growth of high quality InAlN layers, for the case of AlInN/GaN-based DBRs.…”

Section: Motivation For Iii-nitride Tunnel Junction Intracavity Contactsmentioning

confidence: 99%

“…III-nitride vertical-cavity surface-emitting lasers can be divided into two classes: dual dielectric distributed Bragg reflector (DBR) VCSELs, [23][24][25][26][27][28][29][30][31][32][33] and hybrid DBR VCSELs. [34][35][36][37][38][39][40] The later consists of growing the n-side DBR (n-DBR) epitaxially, while dielectric layers are deposited for the p-side DBR (p-DBR).…”

Section: Motivation For Iii-nitride Tunnel Junction Intracavity Contactsmentioning

confidence: 99%

Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

et al. 2016

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We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with IIInitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 µm aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of ~550 µW with a threshold current density of ~3.5 kA/cm 2 , while the ITO VCSELs show peak powers of ~80 µW and threshold current densities of ~7 kA/cm 2 .

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“…If there is residual strain in the underlying structure, for example from epitaxial DBRs, the n-GaN must be grown to a certain thickness to allow for high quality QWs to be grown on top. If an epitaxial lateral overgrowth of the DBR is applied instead, the thickness of the n-GaN will be determined by the ratio between lateral and vertical growth rates in combination with the geometry of the overgrown DBR 29 . If chemical mechanical polishing is used to remove the substrate, the n-GaN will also be thick due to the inaccuracy in the substrate removal process 28 .…”

Section: Cavity Lengthmentioning

confidence: 99%

“…Publications from a few groups followed, and since the first demonstrations there have been a lot of progress in the field of electrically injected III-nitride based VCSELs, both in terms of new technological solutions as well as performance characteristics. 31 To date there are seven groups in the world who have demonstrated lasing under electrical injection [27][28][29][30][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] , and the different approaches and structures are summarized in Table 1. The performance characteristics of published devices, in terms of output power and threshold current density, are plotted in Fig.…”

Section: State-of-the-artmentioning

confidence: 99%

Progress and challenges in electrically pumped GaN-based VCSELs

et al. 2016

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The Vertical-Cavity Surface-Emitting Laser (VCSEL) is an established optical source in short-distance optical communication links, computer mice and tailored infrared power heating systems. Its low power consumption, easy integration into two-dimensional arrays, and low-cost manufacturing also make this type of semiconductor laser suitable for application in areas such as high-resolution printing, medical applications, and general lighting. However, these applications require emission wavelengths in the blue-UV instead of the established infrared regime, which can be achieved by using GaN-based instead of GaAs-based materials. The development of GaN-based VCSELs is challenging, but during recent years several groups have managed to demonstrate electrically pumped GaN-based VCSELs with close to 1 mW of optical output power and threshold current densities between 3-16 kA/cm 2 . The performance is limited by challenges such as achieving high-reflectivity mirrors, vertical and lateral carrier confinement, efficient lateral current spreading, accurate cavity length control and lateral optical mode confinement. This paper summarizes different strategies to solve these issues in electrically pumped GaN-VCSELs together with state-of-the-art results. We will highlight our work on combined transverse current and optical mode confinement, where we show that many structures used for current confinement result in unintentionally optically anti-guided resonators. Such resonators can have a very high optical loss, which easily doubles the threshold gain for lasing. We will also present an alternative to the use of distributed Bragg reflectors as high-reflectivity mirrors, namely TiO2/air high contrast gratings (HCGs). Fabricated HCGs of this type show a high reflectivity (>95%) over a 25 nm wavelength span.

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Room-temperature continuous-wave operation of GaN-based vertical-cavity surface-emitting lasers fabricated using epitaxial lateral overgrowth

Cited by 78 publications

References 18 publications

Milliwatt‐class GaN‐based blue vertical‐cavity surface‐emitting lasers fabricated by epitaxial lateral overgrowth

Milliwatt‐class GaN‐based blue vertical‐cavity surface‐emitting lasers fabricated by epitaxial lateral overgrowth

Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

Progress and challenges in electrically pumped GaN-based VCSELs

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