Evaluation of InAlAs Schottky characteristics grown by MOCVD

Abstract

Schottky characteristics of InAlAs grown by MOCVD has been evaluated. InAlAs Schottky characteristics is strongly affected by MOCVD growth temperature. The reverse current of InAlAs grown at 700°C is more than one order of magnitude larger than that for 750°C. From DLTS measurement, a large signal due to an electron trap with an activation energy of 0.45 eV has been observed in InAlAs grown at 700°C.The results of C-V , Hall and SIMS measurements suggest that the trap is acceptor-type and seems to be related not to impurities but to intrinsic defects. The mechanism of the large reverse current in InAlAs grown at 700°C is thought to be conduction through the trap. I. IntmductionInP-based InAlAdInGaAs high electron mobility transistors (HEMTs) have been developed for the optical communication systems and the wireless communication systems operating at millimeter-wave frequencies '), ' I.Although the InP-based HEMT has shown an excellent high-frequency performance of cut-off frequency over 300GHz 3)9 4), there is still a problem due to poor gate-drain breakdown voltage compared with the GaAs-based HEMT 5), @, which should be a problem from a view point of reliability. One of the reasons for its low gate-drain breakdown voltage is due to the low Schottky barrier height of InAlAs, which is a gate contact layer in InP-based HEMTs. In this paper, we describe the Schottky characteristics of InAlAs depends strongly on the growth conditions of metal organic chemical vapor deposition (MOCVD). II. ExperimentalSi-doped n-type Ino.52Alo.48As layer with the thickness of 1.4pm was grown by MOCVD on a Sdoped n-type (001) InP substrate using trimethylindium (TMI), trimethylaluminum (TMA), arsine (ASH& phosphine (PH3) and disilane (Si2H6) as source gases. The Si doping density was in the range of 4-7~10'~cm.~. The growth temperature was in the range of 680-750°C. The growth rate was 480 &min and the V/III supply ratio was 32-96.To evaluate the Schottky characteristics, AVTi Schottky and the Au-based ohmic electrodes were formed onto the InAlAs layer using EB evaporation. The area of the Schottky electrode was 0.04 mm2. The electrical properties of the grown layers were characterized using current-voltage (1-V), capacitance-voltage (C-V) and Hall measurements. Concentrations of doped Si and unintentionally doped impurities were measured by secondary ion mass spectrometry (SLMS). The deep traps formed within the grown layers were characterized using deep-level transient spectroscopy (DLTS). Figure 1 shows the Schottky characteristics for the InAlAs layers grown at 700°C and 750°C. For the growth temperature of 7OO0C, the Schottky barrier height was lower and the reverse current was more than one order of magnitude larger than that for 750°C. Figure 2 shows the temperature dependence of the Schottky barrier height and the ideality factor obtained from the thermionic emission theory. The Schottky barrier height and the ideality factor were degraded as the temperature decreased, and the temperature dependence for the InAlAs grown at 700...

Study of temperature effects on loss mechanisms in laser diodes with electron stopper layer

“…However, in that case the difficulty is in the growth of Al containing alloys. The typical oxygen concentration in MOCVD grown In 0.52 Al 0.48 As is in the 10 17 -10 18 cm −3 range [5]. It produces deep n-type levels that increase the internal absorption loss and the threshold current density.…”