Biexciton binding in AlxGa1-xN ternary alloys as a function of alloy composition is reviewed on the basis of our recent
experimental observations. The biexciton binding energy in GaN and AlN was evaluated to be 5.6 and 19.3 meV,
respectively. The biexciton binding energy in Ga-rich AlxGa1-xN ternary alloys (x=0.019~0.092) and Al-rich AlxGa1-xN
ternary alloys (x=0.81 and 0.89) was also evaluated on the basis of two-photon absorption of biexcitons. The biexciton
binding energy in Ga-rich ternary alloys increased linearly with aluminum composition and reached to 16.6 meV for
x=0.092. This value was three times as large as the biexciton binding energy in GaN. Similarly, the biexciton binding
energy in Al-rich ternary alloys increased with decreasing aluminum composition and reached to 56 meV for x=0.81. A
strong enhancement of the biexciton binding was observed for both Ga-rich and Al-rich ternary alloys. The enhancement
was attributed to the effect of localization due to alloy disorder. The results indicated that a linear interpolation between
GaN and AlN did not apply to the biexciton binding energy in the ternary alloys. A large bowing existed in the biexciton
binding energy in the ternary alloys.
Excitonic optical properties of Ga-rich AlxGa1-xN ternary alloy epitaxial layers are reviewed on the basis of our recent experimental observations. Photoluminescence due to radiative recombination of biexcitons was clearly observed from the ternary alloys with different aluminum compositions (x=0.019 ~ 0.15). Recombination dynamics of excitons and biexcitons was studied by means of time-resolved photoluminescence spectroscopy. The effect of localization due to alloy disorder on biexcitons was also studied by means of photoluminescence excitation spectroscopy. A Stokes shift of biexcitons was defined experimentally on the basis of two-photon absorption of biexcitons in order to evaluate the degree of biexciton localization quantitatively. A binding energy of biexcitons was determined as a function of aluminum composition. The biexciton localization due to alloy disorder resulted in a strong enhancement of the biexciton binding energy.
The radiative recombination mechanism of InGaN single-quantum- well (SOW) blue light-emitting diodes (LEDs) and InGaN double heterostructure (DH) ultraviolet (UV) LEDs has extensively been investigated by means of the dependence of photoluminescence (PL) and time-resolved PL (TRPL) spectra on an external-electric field. Two emission components are found in the luminescence spectra from each LED on the condition of reverse-bias at 77 K. It is also found that the luminescence intensity of the LEDs decreases dramatically with increasing reverse-bias voltage at room temperature (RT). The model based on field ionization of excitons cannot explain the present experimental phenomena. It is therefore suggested that the free-carrier recombination process is dominant at RT. We have also suggested that these experimental results on the blue and UV LEDs can be explained by the same recombination model. Finally, on the basis of both the experimental ecidence in In0.08Ga0.92N epitaxial layers and strong electron-phonon interaction, the radiative recombination mechanism on InxGa1-xN ternary alloys has been discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.