ELECTRICAL AND OPTICAL CHARACTERIZATION OF GROUP III-V HETEROSTRUCTURES WITH EMPHASIS ON TERAHERTZ DEVICES

Abstract:

Electrical and optical characterizations of heterostructures and thin films based on group III-V compound semiconductors are presented. Optical properties of GaMnN thin films grown by metalorganic chemical vapor deposition (MOCVD) on GaN/Sapphire templates were investigated using IR reflection spectroscopy. Experimental reflection spectra were fitted using a non - linear fitting algorithm, after that the high frequency dielectric constant (e_∞), optical phonon frequencies of E₁(TO) and E₁(LO), and their oscillator strengths (S) and broadening constants (G) were obtained for GaMnN thin films with different Mn fraction. High frequency dielectric constant (e_∞) of InN thin films grown by high pressure chemical vapor deposition (HPCVD) method was also investigated by IR reflection spectroscopy and the average was found to be varying between 7.0 - 8.6. The mobility of free carriers in InN thin films was calculated using the damping constant of the plasma oscillator.

Terahertz detection capability of n-type GaAs/AlGaAs  HEIWIP structures was demonstrated. Threshold frequency (f_c) of 3.2 THz (93 mm) with peak responsivity of 6.5 A/W at 7.1 THz was obtained using a 0.7 mm  thick 1´10¹⁸ cm^-3 n - type doped GaAs emitter layer and a 1 mm thick undoped Al_0.04Ga_0.96As barrier layer. Using n - type doped GaAs emitter layers, the possibility of obtaining small workfunctions (D) required for terahertz detectors has been successfully demonstrated. In addition, the possibility of using GaN (GaMnN) and InN materials for terahertz detection was investigated and a possible GaN base terahertz detector design is presented.

The non - linear behavior of the Inter Pulse Time Intervals (IPTIs) of neuron – like electric pulses triggered by externally in a GaAs/InGaAs  MQW structure at low temperature (~ 10 K) was investigated. It was found that a grouping behavior of IPTIs exists at slow triggering pulse rates. Furthermore, the calculated correlation dimension reveals that dimensionality of the system is higher than the average dimension found in most of natural system.