Studies of InGaAs layers growth by metalorganic chemical vapor deposition for InP-HEMTs; Effects of trimethylindium and triethylindium
We studied an InGaAs epitaxial layers growth by metalorganic chemical vapor deposition (MOCVD) for InP-based high electron mobility transistors (HEMTs). The InGaAs channel layer of HEMTs was grown by a new material combination of triethylindium (TEI), triethylgallium (TEG) and arsine (AsH3). An electron mobility of the HEMTs structure sample was 20% higher than the one grown by trimethylindium (TMI), TEG and AsH3. And the DC characteristics of the HEMTs, the drain current and transconductance, were increased compared with the one. It is confirmed that this growth method is quite effective for the improvement of a characteristics of InP-based HEMTs
Photoluminescence spectra from δ-doped barrier layers in modulation-doped InAlAs/InGaAs field-effect transistor structures
The photoluminescence (PL) spectra from the Si δ-doped InAlAs barrier layers in modulation-doped InAlAs/InGaAs heterostructure field-effect transistor (HFET) structures with contact and recess-etch-stopper layers are investigated. A PL peak associated with the δ-doped layer (δ peak) is found. The δ-peak position shifts to shorter wavelength with increasing δ-doping concentration. The intensity reduction of the δ peak due to raising the temperature from 6 K is considerably slower than that of the exciton peak from the InAlAs buffer layer at about 8100 A, to which confined electrons and holes probably contribute. As a result, the δ-peak overwhelms the exciton peak and becomes the main peak of the InAlAs PL at temperatures higher than 40 K. The δ peak is not detected from HFET structures without the contact and recess-etch-stopper layers. The δ peak is attributed to the recombination of electrons from the δ-doped layer and photogenerated holes confined in the upper side of the barrier layer.
Donor passivation in n-AllnAs layers by fluorine
The mechanism of thermal degradation of both the carrier concentration and mobility in AlInAs layers due to thermally diffused fluorine is discussed. The thermal degradation occurs only in n-type AlInAs layers at temperatures as low as 350°C. In contrast, a similar thermal degradation was never observed for AlInAs containing only acceptor impurities. This phenomenon is explained by the reaction of fluorine atoms with exclusive donor impurities, which forms an ionized fluorine (anion: F−) and results in a reduction in carrier concentration. The created F− ions form a scattering center which leads to a reduction in carrier mobility. Experimental data support that fluorine atoms are of environmental origin and not incorporated during the growth of layers. From further compre-hensive annealing studies for several kinds of (AlGaIn)As material systems, it is found that this donor passivation behavior is peculiar to those compounds which contain both AlAs and InAs.