Low-temperature scanning-tunneling microscope for luminescence measurements in high magnetic fields

We have designed and built a low-temperature (1.3-4.2 K) scanning-tunneling microscope which is capable of collecting light that is generated in the t unneling region. Light collection is done by means of two fibers whose clea ved front is in close proximity (approximate to1 mm) to the tunneling regio n. The whole system can be operated in high magnetic fields (11 T) without loss of optical signal strength. As a demonstration, we measured the electr oluminescence spectra of an InGaAs quantum well at various temperatures. At 4.2 K, we found an electron-to-photon conversion factor that is three orde rs of magnitude higher than at room temperature. (C) 2001 American Institut e of Physics.