Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

Abstract

We report on green (550–560 nm) electroluminescence (EL) from (Al0.5Ga0.5)0.5In0.5P-(Al0.8Ga0.2)0.5In0.5P double p-i-n heterostructures with monolayer-scale GaP insertions in the cladding layers and light-emitting diodes based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. At moderate current densities (∼500 A/cm2), the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (∼550 nm at room temperature). At high current densities (>1 kA/cm2), a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4 kA/cm2, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14 kA/cm2. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure, which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p-doped (Al0.8Ga0.2)0.5In0.5P cladding layers.

Room-temperature yellow-orange (In,Ga,Al)P–GaP laser diodes grown on (n11) GaAs substrates

“…As noted for the structure grown side by side on (811)A substrate self-organized corrugated quantum wire arrays were observed in the gain region, as it was already discussed previously [15,18]. The (811)A-grown structure emitted however at ~15 nm longer wavelengths than those grown on (211) and (322) and demonstrated no lasing at room temperature.…”

“…The ε zz maps of the barriers indicate that the 4 nm-thick in-plane tensile strained layers contain about 40% of indium that was deduced by using elasticity theory and Vegard's law. We note that some broadening of the interfaces and Indium intermixing with the surrounding matrix can be attributed (at least partially) to the periodic interface corrugation of the (112) surface [27], as even submonolyaer GaP insertions could be resolved in similar structures grown on the (118) surface [17,18]. The ε xx maps in the barriers demonstrate the presence of vertical columnlike in-plane strain variation with amplitude of ∼ ± 0.2% and a period of ∼30 nm.…”

“…However, no information was provided on the substrate orientation, the compositions and thicknesses of the cladding layers used for the optical and electron confinement, the cavity length and facet coating. Recently, it was reported that (In,Ga,Al)P light-emitting diodes grown on highindex GaAs substrates inclined from (100) towards <111>-crystallographic direction and containing tensile strained ultrathin GaP insertions showed an improved intensity of the electroluminescence at room temperature in the green spectral range of ~568 nm [19] as compared to (100)-grown devices [17,18]. The effect was attributed to the enhanced barrier heights in the conduction band for ultrathin tensile strained GaP barriers formed on surfaces close to the (111) GaAs orientation.…”

New orientations in the stereographic triangle for self-assembled faceting

“…By contrast, HI orientations that lie on the edges of the ST connecting the LI (100) plane to the (111) or (110) planes -such as the (210), (311), and (211) planes-produce surface structures composed of three or more facets. 2,11,14,18 Because HI surfaces within the ST have complex bulk-truncated atomic arrays, only a few of these GaAs planes have been studied for 1DPA formation: the (631), (731), and (531) planes. 7,19,20 Due to this complexity, it is also quite remarkable that some authors have found energetically stable surfaces inside the ST for crystals such as Si, Ge, and GaAs.…”

Application of nanophotonics to the next generation of surface-emitting lasers

“…The use of InGaAs quantum wells (QW) and quantum dots [6] in combination with the antiguiding VCSEL concept [7] has solved the problem of reliable highspeed oxide-confined VCSELs [8,9] at 850 nm and longer wavelengths. By applying tensile strained wide bandgap layers and the proper use of substrate orientation, potential barriers in the conduction band may be created by preventing leakage of the injected nonequilibrium electrons into the p-doped cladding layers [10]. Presently, the antiguiding VCSEL approach, which allows to increase the oscillator strength of the optical transition [11] due to the suppressed in-plane modes and an option of ultimately narrow λ/2 cavity, is used by key VCSEL manufacturers.…”