We herein describe our investigation of the superconducting and magnetic properties of the rare-earth ternary germanide intermetallic compounds La 2 Pt 3 Ge 5 and Pr 2 Pt 3 Ge 5 . Single crystals of La 2 Pt 3 Ge 5 and Pr 2 Pt 3 Ge 5 were synthesized using the high temperature metal flux method.Both types of crystal formed in a U 2 Co 3 Si 5 -type orthorhombic structure (space group Ibam). La 2 Pt 3 Ge 5 showed the onset of superconducting phase transition at T c = 8.1 K, which, to the best of our knowledge, is the highest T c of all the RE 2 T M 3 X 5 (RE = Rare Earth elements, T M = Transition metal, and X = s − p metal) superconductors, and from the specific heat data, it was found to have multi-gap superconductivity. Pr 2 Pt 3 Ge 5 showed both a superconducting phase transition at T c = 7.8 K and two antiferromagnetic transitions at T N 1 = 3.5 K and T N 2 = 4.2 K, which indicates the coexistence of superconductivity and magnetism. However, the correlation between the superconductivity and the magnetism was too weak to be observed. In its normal state, Pr 2 Pt 3 Ge 5 revealed strong magnetic anisotropy, probably due to the crystalline electric field effect.

We demonstrated the long wavelength (485nm) lasing of InGaN laser diodes under continuous wave condition at room temperature over 10mW. Two InGaN laser structures were adapted with different indium composition for InGaN optical confinement layers (OCLs) below quantum wells. The blue shift of electroluminescence (EL) was reduced in InGaN laser diodes grown on 3% In concentration in InGaN OCL compared with 1.5% In concentration in InGaN OCL. The EL peak for laser diode with 3% In concentration in InGaN OCL occurs at longer wavelength for all current levels compared to the laser with 1.5% In concentration in InGaN OCL. In addition, the laterally nonuniform InGaN wells grown on 1.5% In concentration in InGaN OCL was verified by the cross-sectional view of InGaN active layer using high-resolution transmission electron microscopy.

The authors analyzed radiative efficiency of InGaN laser diodes (LDs) emitting at 405nm. Based on semiconductor rate equations, the radiative efficiency is unambiguously determined by the analysis of electroluminescence characteristics. The radiative efficiency exceeds 70% even far below threshold of ∼3mA at a high temperature of 80°C. This highly radiative characteristic is attributed to reduced contribution of nonradiative recombination in LDs with low-dislocation-density active material. It is also found that the radiative efficiency is almost independent of threshold current, indicating that nonradiative recombination is not a major factor which determines lasing threshold in 405nm emitting InGaN LDs having low dislocation density.

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We investigated the inhomogeniety of InGaN quantum wells (QWs) with high In content in the GaNbased blue laser diodes (LDs). The 2QWs LD structure show the twice higher photoluminescence intensity and the slightly higher electroluminescence intensity than single quantum well (SQW) LD. However, we can obtain the high power blue InGaN SQW LDs with the low threshold current density of 2.19 kA/cm 2 and the high sloped efficiency of 0.8 W/A at the cw condition by reducing the number of QWs. From carrier distribution by simulation, blue InGaN 2QWs LDs represented the non-uniformed hole distribution of n-side 1 st and p-side 2 nd well in InGaN/InGaN 2QWs region due to the low hole concentration and mobility of p-type nitrides. From time-resolved photoluminescence (TRPL), we obtained that 2QWs LD shows the some spatial localization states due to the multiple component PL decay process. Therefore, we can guess that the inhomogeniety of InGaN QWs would be quite restricted in deep InGaN QWs of GaN based blue LDs which results in significantly in homogeneities of QWs. 1 Introduction III-nitrides have attracted much attention for optoelectronic device applications whose emission wavelengths ranging from green to ultraviolet light due to their wide band gap [1][2][3]. Especially, GaN based blue-violet laser diodes with emission wavelength of 405 nm have attracted interest as light source for next generation digital versatile disk application. In addition to this optical storage application [4,5], GaN based blue LDs for the full color laser displays have also been developed [6]. A lot of research groups have reported the difficulties of high efficiency in the blue/green light emitting InGaN based device by the followings; the significantly high vapor pressure of nitrogen over InGaN and the high volatility of In at a high growth temperature, the increase of non-radiative recombination center as the point defect, and the existence of strain induced piezoelectric field [1][2][3]. Additionally, in order to achieve the longer wavelength, the uniformity of InGaN MQWs is more deteriorated with increasing the In content as well as the number of well in the laser diode structure [7]. In this study, we report the spontaneous and the stimulated emission properties related to the inhomogeniety of blue InGaN QWs with high In content in the laser diode structure.