The δ-Doped In_0.25Ga_0.75As/GaAs Pseudomorphic High Electron Mobility Transistor Structures Prepared by Low-Pressure Metal Organic Chemical Vapor Deposition^*

Abstract

The (800 Å)GaAs/In 0.25 Ga 0.75 As/(0.5 µm) GaAs strain layers with δ-doping in the GaAs cap layer were fabricated without using AlGaAs layers. Triethylgallium (TEG), trimethylindium (TMI), arsine (AsH 3 ) and silane (SiH 4 ) were used as the sources and dopants in these structures grown by the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique for the first time to study these structures. The δ-doping was obtained by a stop-growth process by which a very thin and heavily doped layer (1.86×10 13 cm -2 ) can be realized. For the (δ-doped) GaAs/In 0.25 Ga 0.75 As/GaAs high electron mobility transistor (HEMT) structures, the concentration of two-dimensional electron gas (2-DEG) and the Hall mobilities were investigated. Experimental results show that a structure with (80 Å) In 0.25 Ga 0.75 As as the active channel and with a 70 Å spacer layer revealed the highest 2-DEG concentration and mobility product of 5.5times10 16 V -1 ·s -1 at a temperature of 77 K. These structures are easy to achieve by the LP-MOCVD mechod and are promising for high-performance field effect transistors (FETs).