III-V-based semiconductor quantum structures for mid-infrared light emitting devices

在近红外和中红外波长范围发射的紧凑型光源在医学成像和诊断、远程痕量气体和空气污染监测以及电信方面具有潜在的应用。根据应用的不同，这些设备可能需要在非常窄的波长范围内发射，或者需要宽光谱输出，例如用于光学相干层析成像。可能还需要调整输出波长。基于III-V化合物半导体的器件可以满足许多这样的应用。器件通常使用在标准III-V二进制衬底上沉积的外延层结构来制造，通常是GaAs、InP或GaSb。基于目标波长选择衬底，并且使用组成更复杂的III族和V族元素层的多个晶格匹配和/或薄应变层来生长器件结构。这些二元衬底的使用限制了晶格匹配组合物的范围，从而限制了可获得的波长范围。克服这一限制的一种方法是使用变形衬底层(MSL)，它包括以一种松弛应变的方式生长三元或四元III-V层的厚应变层，而不会引起线位错，并产生无缺陷的表面层，由于其不同的晶格常数，可以生长层，以用于以以前无法访问的波长制造器件。这可以应用于基于量子井、量子线(QWR)和量子点(QD)的器件。这项研究提出了使用MSL方法设计、制造和表征可发射高达3微米的光源，具体目标是利用成熟的InGaAsP四元化合物，这些化合物非常适合于器件制造。基于QWR和QD的器件也将被制造出来，以利用与此类器件的降维相关的固有优势。

Compact light sources that emit in the near- and mid-infrared wavelength range have potential applications in medical imaging and diagnostics, remote trace gas and air pollution monitoring, and telecommunications. Depending on the application these devices may need to emit over a very narrow wavelength range or require a broad spectral output such as used for Optical Coherence Tomography. It may also be necessary to tune the output wavelength. III-V compound semiconductor-based devices can satisfy many such applications. Devices are usually fabricated using epitaxial layer structures deposited on standard III-V binary substrates; typically GaAs, InP or GaSb. The substrate is chosen based on the target wavelength and the device structure is grown using multiple lattice-matched and/or thin strained layers of compositionally more complex layers of the group III and group V elements. The use of these binary substrates limits the range of lattice-matched compositions and hence the range of wavelengths accessible. A way to overcome this limitation is to use metamorphic substrate layers (MSL) which involves growing thick strained layers of ternary or quaternary III-V layers in a way that relaxes the strain, without causing threading dislocations, and producing a defect-free surface layer that, because of its different lattice constant, can allow layers to be grown for producing devices at previously inaccessible wavelengths. This can be applied to quantum well, quantum wire (QWR) and quantum dot (QD) based devices. This research proposes the design, fabrication and characterization of light sources that can emit at up to 3µm using the MSL approach with the specific goal of utilizing the well established InGaAsP quaternary compounds which are well developed for device manufacturing. QWR and QD based devices will also be fabricated to exploit the inherent advantages associated with the reduced dimensionality of such devices.