Investigation of active-region doping on InAs/GaSb long wave infrared detectors

The eight-band κ·p model is used to establish the energy band structure model of the type-II InAs/GaSb superlattice detectors with a cut-off wavelength of 10.5μm,and the best composition of M-structure in this type of device is calculated theoretically.In addition,we have also experimented on the devices designed with the best performance to investigate the effect of the active region p-type doping temperature on the quantum efficiency of the device.The results show that the modest active region doping temperature(Be:760℃)can improve the quantum efficiency of the device with the best performance,while excessive doping(Be:>760℃)is not conducive to improving the photo response.With the best designed structure and an appropriate doping concentration,a maximum quantum efficiency of 45% is achieved with a resistance-area product of 688?·cm^2,corresponding to a maximum detectivity of 7.35×10^11cm·Hz^1/2/W.     

基于锑化物二类超晶格的多色红外探测器研究进展

近年来InAs/GaSb二类超晶格红外探测器在材料晶体结构生长、器件结构设计与成像应用方面取得了飞速发展。尤其在多色红外探测方面,二类超晶格材料以其具备的带隙可调、暗电流小、量子效率高、材料均匀性高,以及成本低等优越性能,使其逐步成为第三代红外焦平面探测器的优选材料。本文阐述了锑化物窄带隙半导体研究中心的锑化物多色红外探测器研究进展。本团队成功实现了低噪声、高量子效率以及低光学串扰的短/中、短/长、中/长、长/长、中/长/甚长波等多种高性能多色红外探测器研制。     

Two-dimensional electron gas characteristics of InP-based high electron mobility transistor terahertz detector

The samples of In_xGa_(1-x)As/In_(0.52)Al_(0.48)As two-dimensional electron gas(2DEG)are grown by molecular beam epitaxy(MBE).In the sample preparation process,the In content and spacer layer thickness are changed and two kinds of methods,i.e.,contrast body doping andδ-doping are used.The samples are analyzed by the Hall measurements at 300 Kand 77 K.The In_xGa_(1-x)As/In_(0.52)Al_(0.48)As 2DEG channel structures with mobilities as high as 10289 cm~2/V·s(300 K)and42040 cm~2/V·s(77 K)are obtained,and the values of carrier concentration(Nc)are 3.465×10~(12)/cm~2and 2.502×10~(12)/cm~2,respectively.The THz response rates of In P-based high electron mobility transistor(HEMT)structures with different gate lengths at 300 K and 77 K temperatures are calculated based on the shallow water wave instability theory.The results provide a reference for the research and preparation of In P-based HEMT THz detectors.     

GaAs Based InAs/GaSb Superlattice Short Wavelength Infrared Detectors Grown by Molecular Beam Epitaxy

InAs/GaSb superlattice （SL） short wavelength infrared photoconduction detectors are grown by molecular beam epitaxy on GaAs（O01） semi-insulating substrates. An interfacal misfit mode AISb quantum dot layer and a thick GaSb layer are grown as buffer layers. The detectors containing a 200-period 2 ML/S ML InAs/GaSb SL active layer are fabricated with a pixel area of 800×800 μm^2 without using passivation or antirefleetion coatings. Corresponding to the 50% cutoff wavelengths of 2.05μm at 77K and 2.25 μm at 300 K, the peak detectivities of the detectors are 4 × 10^9 cm·Hz^1/2/W at 77K and 2 × 10^8 cm·Hz1/2/W at 300K, respectively.     

量子点单光子源的光纤耦合

半导体量子点在低温下产生谱线细锐的激子发光可制备单光子源.光纤耦合可避免低温共聚焦装置扫描定位和振动影响,是实现单光子源即插即用和组件化的关键技术.在耦合工艺上,基于微区定位标记发展出拉锥光纤与光子晶体腔或波导侧向耦合、大数值孔径锥形端面光纤与量子点样片垂直耦合等技术;然而,上述工艺需要多维度精密调节以避免柔软光纤的畸形弯曲实现对准和高效耦合.陶瓷插针或石英V槽封装的光纤无弯曲且具有大平滑端面,只要与单量子点样片对准贴合就可保证垂直收光, V槽封装的排式光纤还可通过盲对粘合避免扫描对准,耦合简单.本文在前期排式光纤粘合少对数分布Bragg反射镜(distributed Bragg reflector, DBR)微柱样片实现单光子输出基础上,经理论模拟采用多对数DBR腔提升样片垂直出光和光纤收光效率,使光纤输出单光子计数率大大提升.     

Temperature Dependence of Photoluminescence from Single and Ensemble InAs/GaAs Quantum Dots

We investigate the temperature dependence of photoluminescence from single and ensemble InAs/GaAs quantum dots systematically. As temperature increases, the exciton emission peak for single quantum dot shows broadening and redshift. For ensemble quantum dots, however, the exciton emission peak shows narrowing and fast redshift. We use a simple steady-state rate equation model to simulate the experimental data of photoluminescence spectra. It is confirmed that carrier-phonon scattering gives the broadening of the exciton emission peak in single quantum dots while the effects of carrier thermal escape and retrapping play an important role in the narrowing and fast redshift of the exciton emission peak in ensemble quantum dots.     

Effect of Annealing on Structural and Magnetic Properties of a Thick （Ga,Mn）As Layer

We investigate effects of annealing on magnetic properties of a thick (Ga,Mn)As layer, and find a dramatic increase of the Curie temperature from 65 to 115K by postgrowth annealing for a 500-nm (Ga,Mn)As layer.Auger electron spectroscopy measurements suggest that the increase of the Curie temperature is mainly due to diffusion of Mn interstitial to the free surface. The double-crystal x-ray diffraction patterns show that the lattice constant of (Ga,Mn)As decreases with increasing annealing temperature. As a result, the annealing induced reduction of the lattice constant is mainly attributed to removal of Mn interstitial.     

半导体带间级联激光器研究进展

半导体带间级联量子阱是实现3~5μm波段中红外激光器的重要前沿,其在半导体光电器件技术、气体检测、医学医疗以及自由空间光通信等诸多领域具有重要科学意义和应用价值。半导体带间级联量子阱发光机理是以二类量子阱中的电子与空穴的带间辐射复合发光为主导,再通过电子注入区与空穴注入区形成级联放大,实现多个量子阱周期内电子与空穴的重复利用。本文综述了半导体带间级联激光器从提出能带结构、外延材料到器件制备技术的发展历程,剖析了器件结构各功能区基本概念和工作原理,介绍了器件结构设计与制备工艺技术难点的里程碑突破,详细解释了载流子再平衡、分别限制层等设计,最后展望了半导体带间级联激光器的发展方向和趋势。     

分子束外延生长的InAs/GaAs自组织量子点发光特性

研究了分子束外延生长的覆盖了1nm的InxAl1-xAs(x=0．2．0．3)和3nm的In0.2Ga0.8As复合应力缓冲层InAs／GaAs自组织量子点(QD)光致发光(PL)特性。加InAlAs层后PL谱红移到1．33μm．室温下基态和第一激发态间的跃迁能级差增加到86meV。高In组份的InAlAs有利于获得较长波长和较窄的半高宽(FWHM)。对于覆盖复合应力缓冲层的QD不会使波长和FWHM发生显著变化，但可以使基态和第一激发态间的能级差进一步增大。这些结果归因于InAlAs能够有效的抑制In的偏析，减少应力．使QD保持较高的高度。同时．由于InAlAs具有较高的限制势垒，可以增加基态和第一激发态间的能级差。     

1.3微米发光自组织InAs/GaAs量子点的电致发光研究

用优化的MBE参数生长了1.3μm发光的InAs/GaAs量子点材料，并制成发光二极管，对不同温度和有源区长度下样品的电致发光谱进行了细致的研究。观察到两个明显的电致发光峰，分别对应于量子点基态和激发态的辐射复合发光，实验表明，由于能态填充效应的影响适当增大量子点发光器件有源区长度，更有利于获得基态的光发射，这个结果提供了一种控制和调节InAs/GaAs量子点发光二极管和激光器的工作波长的方法。