Photoluminescence excitation spectroscopy of InAs0.67P0.33/InP strained single quantum wells

The optical emission characteristics of biaxially compressed InAs _x P_{1− x} /InP strained single quantum well (QW) structures, with nominal compositionx=0.67, have been investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The highly strained QWs exhibit intense and narrow PL in the 0.9–1.5 μm wavelength range, similar to the lattice-matched InGaAs(P)/InP system. The 20 K PLE spectra exhibit well-resolved features attributed ton=1 heavy hole (E1H1) and light hole (E1L1) transitions in the 1.0–1.5 μm wavelength range. In addition, features attributed to transitions betweenn=2 electrons and heavy holes (E2H2), and betweenn=1 electrons and unconfined holes (E1Hf), were observed. The energy splitting between the heavy-hole and light-hole bands was found to be a sensitive measure of the band offsets in the system. The best prediction of this splitting was obtained for a valence band offset of δE _V ∼0.25δE _G . This value of band offset was in agreement with the energy position of the E1Hf transition. The observed transition energies were also compared with the results of a finite square well model, taking into account the effects of strain, and the results offer further support for the band offset assignment. This study indicates that the InAsP system may be advantageous for application in strained-layer optoelectronic devices operating in the 1.3–1.6 μm wavelength range.     

CdSe量子点的制备与荧光特性研究

主要讨论了CdSe量子点的制备及荧光特性。CdSe量子点由化学方法制备，通过选择不同的反应时间得到不同尺度的量子点样品。用荧光方法研究了量子点样品在石英衬底和有机溶剂中的荧光特性。实验表明，这些量子点都有良好的荧光特性。还用无限深球方势阱模型分析了量子点样品的电子态，并根据荧光参数估算了量子点的尺度．各样品荧光峰具有一致的半峰宽，表明CdSe量子点的成核过程在反应开始时同时完成。     

Growth and characterization of GaSb bulk crystals with low acceptor concentration

GaSb bulk single crystals with low acceptor concentration were grown from a bismuth solution by the traveling heater method. The result is isoelectronic doping by Bi which gives a variation of the opto-electronic properties as a function of grown length as well as a pronounced microscopic segregation. Photoluminescence spectra at 4K show a decrease of the natural acceptor during growth, which is confirmed by Hall measurements. The electrical properties of this isoelectronic doped GaSb are hole concentrations and mobilities of N_A − N_D = 1.7 × 10¹⁶ cm⁻³ and μ = 870 cm²Vs at room temperature and N_A-N_D = 1 × 10¹⁶ cm⁻³ and μ = 4900 cm²/Vs at 77K, respectively. The lowest p-type carrier concentration measured at 300K is N_A − N_D = 3.3 × 10¹⁵ cm⁻³     

掺富勒烯SiO2气凝胶的制备与发光性质研究

本文利用溶胶－凝胶工艺成功地将富勒烯掺入了ＳｉＯ２气凝胶的纳米孔洞中，在Ａｒ＾＋离子激光激发下，观察到了很强的可见光发射，对该现象作了初步的解释。     

Electrical and optical properties of oxygen doped GaN grown by MOCVD using N2O

Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N₂O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried ammonia using nitrogen (N₂) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface. Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N₂O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations in the range of 4×10¹⁶ cm⁻³ to 4×10¹⁸ cm⁻³ as measured by Hall effect. The observed carrier concentration increased with increasing N₂O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B exciton emission an exciton bound to a shallow donor. With increasing N₂O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons. These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius and electronegativity arguments.     

Hg_（1－x）Cd_xTe的扫描光致发光研究

用傅里叶变换红外扫描光致发光方法研究了Ｈｇ１－ｘＣｄｘＴｅ体单晶样品，该方法可直接得到ＨｇＣｄＴｅ晶片组分的二维平面分布，并可得到辐射复合在复合机制中所占比重的平面分布，以及晶体中非平衡载流子寿命的分布     

MOCVD生长的CdZnTe／ZnTe多量子附的激子光学特性

用常压ＭＯＣＶＤ方法在ＧａＡｓ（１００）衬底上生长了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱。在室温下，观测到了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的三个谱带发光。根据ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的吸收光谱和不同激发光强下的发光光谱，分别归结ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱中观测到的三个发光谱带于覆盖层发光、ｎ＝１的重空穴激子发光及杂质发光。     

Fast full‐color reflective display via photoluminescent enhancement

Reflective displays are advantageous in applications requiring low power or daylight readability. However, there are no low‐cost reflective technologies capable of displaying bright colors. By employing photoluminescence to more efficiently use ambient light, we created a prototype display that provides bright, full color in a simple, low‐cost architecture. This prototype includes a novel electrokinetic shutter, a layer that incorporates patterned luminescent red, green, and blue sub‐pixel elements, and a novel optical out‐coupling scheme. The luminescent elements convert otherwise‐wasted portions of the incident spectrum to light in the desired color band, resulting in improved color saturation and lightness. This prototype provides a color gamut that is superior to competing reflective display technologies that utilize color filters in single‐layer side‐by‐side sub‐pixel architectures. The current prototype is capable of switching in <0.5 s; future displays based on an alternative electro‐optic shutter technology should achieve video rate operation. A transflective version of this technology has also been prototyped. The transflective version utilizes its backlight with a power efficiency that is at least three times that of a conventional liquid crystal display. These photoluminescence‐based technologies enable a host of applications ranging from low‐power mobile products and retail pricing signage to daylight readable signage for outdoor advertising segments.     

Long-lasting photoluminescence quantum yield of cesium lead halide perovskite-type quantum dots

Cesium lead halide perovskite(CsPbX₃,X=Cl,Br,I)quantum dots(QDs)and their partly Mn²⁺-substituted QDs(CsPb1–xMnxX3)attract considerable attention owing to their unique photoluminescence(PL)efficiencies.The two types of QDs,having different PL decay dynamics,needed to be further investigated in a form of aggregates to understand their solid-state-induced exciton dynamics in conjunction with their behaviors upon degradation to achieve practical applications of those promising QDs.However,thus far,these QDs have not been sufficiently investigated to obtain deep insights related to the long-term stability of their PL properties as aggregated solid-states.Therefore,in this study,we comparatively examined CsPbX₃-and CsPb1–xMnxX₃-type QDs stocked for>50 d under dark ambient conditions by using excitation wavelength-dependent PL quantum yield and time-resolved PL spectroscopy.These investigations were performed with powder samples in addition to solutions to determine the influence of the inter-QD interaction of the aged QD aggregates on their radiative decays.It turns out that the Mn²⁺-substituted QDs exhibited long-lasting PL quantum efficiencies,while the unsubstituted CsPbX₃-type QDs exhibited a drastic reduction of their PL efficiencies.And the obtained PL traces were clearly sensitive to the sample status.This is discussed with the possible interaction depending on the size and distance of the QD aggregates.     

Surface modification of K2TiF6:Mn4+ phosphor with SrF2 coating to enhance water resistance

K₂TiF₆:Mn⁴⁺ is an attractive narrow-band red-emitting phosphor for warm white light-emitting diodes (LEDs). Nevertheless, the hexafluoride phosphor is liable to deliquesce in moist environments, which leads to a sharp deterioration performance of luminescence. Surface modification of K₂TiF₆:Mn⁴⁺ phosphor with SrF₂ coating has been introduced, with the aid of KHF₂ transition layer to moderate the lattice mismatch. The reaction mechanism is discussed in detail, as so as the influence of SrF₂ coating on the luminescence intensity. The SrF₂ coating is able to prevent the hydrolysis of internal [MnF₆]²⁻ group; thereby, the luminescence intensity retains over 90% of initial value after being immersed in distilled water for 2 h. The LED devices fabricated with commercial Y₃Al₅O₁₂:Ce³⁺ and as-modified K₂TiF₆:Mn⁴⁺ phosphors exhibit bright white light with tunable chromaticity coordinate, correlated color temperature, and color rendering index. It enlightens a convenient method to enhance the moisture resistance of Mn⁴⁺ doped fluoride phosphors for commercial application in the field of white LEDs.