Semiconductor heterojunctions, first introduced around 50 years ago, have seen remarkable growth and led to numerous applications. They are the basic building blocks of many of the most advanced electronic and optoelectronic devices, such as high-speed transistors and semiconductor lasers, which have significant impacts on information and communication technology. In 2000, Dr. Zhores Alferov and Dr. Herbert Kroemer were awarded the Nobel Prize in Physics for developing semiconductor heterostructures used in high-speed- and opto-electronics.
In this talk, I will start with a few basic issues of semiconductor heterojunctions, such as heterojunction formation, band offsets and the device applications. I will then give an overview on the research projects that I have been doing in the past decade, which include the determination of band offsets of II-VI compound semiconductor heterojunctions by using synchrotron radiation photoemission, the design and fabrication of quantum cascade laser for Terahertz emission, the design and demonstration of semiconductor infrared optical up-converter and the applications of novel scanning probe microscopy technologies to probing the inner workings of active semiconductor devices at nanometer scales. I will show that the projects, even though they look different from one another, have direct or indirect connections with the concept of the semiconductor heterojunction. I will also briefly talk about my future research plan if time allows.