Dependence of InN properties on MOCVD growth parameters

Abstract

In order to optimize the growth conditions, the effect of the most important growth parameters such as growth temperature, pressure and V/III ratio on MOCVD‐grown InN was investigated. A series of samples were grown by changing the growth temperature from 500 °C to 550 °C at fixed growth pressure of 800 mbar and V/III ratio of 145000. An improvement of electrical properties with temperature increment was noted. The highest mobility of 1200 cm2/Vs was achieved at 550 °C with a bulk carrier concentration of 4.32 x 1018 cm‐3. The effect of V/III ratio on In droplet formation and on carrier concentration was also studied. At fixed temperature of 520 °C, reactor pressure of 200 mbar and at fixed NH3 flow of 3 slm, a rising TMIn flow from 1.2 µmol/min to 2.0 µmol/min results in a carrier concentration increment from 6.06 x 1018 cm‐3 to 1.33 x 1019 cm‐3and a decrement of the mobility from 430 cm2/Vs to 348 cm2/Vs. X‐ray diffraction measurements show that the intensity associated with In droplets on the surface is rising with increasing TMIn flow. The effect of reactor pressure on InN growth was also examined. A high sensitivity to growth pressure for crystalline quality of InN was observed. The full width at half maximum (FWHM) values of InN (0002) reflexes decreased with increasing reactor pressure. With increasing growth pressure above 200 mbar, FWHM of around 275 arcsec of InN (0002) was achieved. This FWHM value is the lowest reported in literature for MOCVD‐grown InN so far. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural, electrical and optical characterization of MOCVD grown In-rich InGaN layers

“…This is attributed to a high degree of atomic disorder, the large atomic radius difference between In and Ga, and phase separation [19,20]. The FWHM value for InN (0002) is much higher than that reported before (270 arcs) [2]. The high growth temperature (550 1C) employed could be the reason for the low crystal quality [2].…”

“…The FWHM value for InN (0002) is much higher than that reported before (270 arcs) [2]. The high growth temperature (550 1C) employed could be the reason for the low crystal quality [2]. For the strain state investigation, RSM for (10-15) diffractions was performed.…”

“…The band gap of InGaN alloys which spans a wide range of energies from 0.64 eV (InN) (near-infrared) to 3.44 eV (GaN) (near UV) [2][3][4][5] makes this material beneficial in solar cell technology [6,7]. Growing high quality In-rich InGaN layers remains a challenge due to a large thermal stability difference and also the large difference in inter-atomic spacing between InN and GaN [8].…”

Point defect evolution in low‐temperature MOCVD growth of InN

“…This indicates an increase in positron trapping at vacancy‐type defects. The turning point at about half of the layer thickness 18 is caused by positrons annihilating in the GaN template and confirms well the layer thickness determined by cross‐sectional SEM, i.e ., 300 ± 30 nm 4. In sample No.1 no such profile is visible and the S ‐parameter approaches with higher implantation energies directly the GaN bulk value in the GaN template.…”

“…While highest purity material can be deposited by plasma‐assisted (PA) molecular beam epitaxy (MBE) 3, the development of a growth process utilizing metal‐organic chemical vapor deposition (MOCVD) is strongly desirable for industrial application due to the good scalability of the latter. Although strong improvements in this area could be achieved during recent years 4, 5 the quality of MOCVD grown material remains still somewhat inferior with electron concentrations in the mid‐10 18 cm −3 , about one magnitude larger than in state‐of‐the‐art PA‐MBE grown InN layers 3. Both, point defects such as nitrogen vacancies (V N ) and interstitials (N I ), as well as hydrogen impurities introduced in MOCVD growth through the use of NH 3 as the nitrogen source have been proposed as the responsible donors behind the increased electron concentrations in as‐grown MOCVD InN 6–9.…”