Abstract: An iron-doped indium phosphide or gallium arsenide semiconductor laser. The emiconductor material is doped when formed by uniformly distributing transition metal ions such as iron throughout the semiconductor. The concentration of the iron ions is from about 1.times.10.sup.15 to about 1.times.10.sup.18 ions per cubic centimeter, but is limited only by the solubility of iron indium phosphide or gallium arsenide. It has been determined that the greater the concentration of ions, the easier the laser emission is obtained. At liquid helium temperature, the iron-doped semiconductor laser will operate at a wavelength near 3 microns.

Abstract: This invention is directed to a device and method for measuring carrier mlity and density in thin-film semiconductor materials such as those used in thin-film circuitry, particularly in high-frequency microwave devices. The device includes a microwave system in combination with a variable magnetic field in which the material to be measured is positioned at an E-field maximum in a shorted section of waveguide, which shorted section is in the magnetic field. The magnetic-field dependence of the reflected power is then monitored. The carrier mobility is derived from the value of the magnetic field at the point at which the microwave power reflected from the material falls to one-half of the reflected microwave power when the magnetic field value is zero. The electron density may be determined from the change in amplitude of the signal between zero magnetic field and high fields by proper calibration.