[PDF]    http://dx.doi.org/10.3952/physics.v55i4.3221

Open access article / Atviros prieigos straipsnis

Lith. J. Phys. 55, 255–263 (2015)
ENHANCEMENT OF QUANTUM EFFICIENCY IN InGaN QUANTUM WELLS BY USING SUPERLATTICE INTERLAYERS AND PULSED GROWTH
Kazimieras Nomeika, Mantas Dmukauskas, Ramūnas Aleksiejūnas, Patrik Ščajev, Saulius Miasojedovas, Arūnas Kadys, Saulius Nargelas, and Kęstutis Jarašiūnas
Institute of Applied Research, Vilnius University, Saulėtekio 9, LT-10222 Vilnius, Lithuania
E-mail: kazimieras.nomeika@tmi.vu.lt

Received 22 June 2015; revised 21 July 2015; accepted 29 September 2015

Enhancement of internal quantum efficiency (IQE) in InGaN quantum wells by insertion of a superlattice interlayer and applying the pulsed growth regime is investigated by a set of time-resolved optical techniques. A threefold IQE increase was achieved in the structure with the superlattice. It was ascribed to the net effect of decreased internal electrical field due to lower strain and altered carrier localization conditions. Pulsed MOCVD growth also resulted in twice higher IQE, presumably due to better control of defects in the structure. An LED (light emitting diode) structure with a top p-type contact GaN layer was manufactured by using both growth techniques with the peak IQE equal to that in the underlying quantum well structure. The linear recombination coefficient was found to gradually increase with excitation due to carrier delocalization, and the latter dependence was successfully used to fit the IQE droop.
Keywords: light emitting diodes, nitride semiconductors, photoluminescence, carrier recombination, carrier diffusion
PACS: 73.21.Fg, 78.67.-n, 78.47.-p

KVANTINIO NAŠUMO PAGERINIMAS InGaN KVANTINĖSE DUOBĖSE ĮTERPIANT SUPERGARDELĘ IR NAUDOJANTIS IMPULSINIU AUGINIMU
Kazimieras Nomeika, Mantas Dmukauskas, Ramūnas Aleksiejūnas, Patrik Ščajev, Saulius Miasojedovas, Arūnas Kadys, Saulius Nargelas, Kęstutis Jarašiūnas
Vilniaus universiteto Taikomųjų mokslų institutas, Vilnius, Lietuva

Vidinio kvantinio našumo (VKN) pagerinimas InGaN kvantinėse duobėse dėl supergardelės įterpimo ir impulsinio auginimo pritaikymo ištirtas laikinės skyros optinių metodikų kombinacija. Supergardelės tarpsluoksnio įterpimas padidino VKN tris kartus, tai gali būti aiškinama sumažėjusiu vidiniu elektriniu lauku dėl mažesnių įtempimų ir pakeistų lokalizacijos sąlygų. Impulsinio auginimo dėka VKN padidėjo dvigubai, tikimiausiai dėl geresnės defektų kontrolės struktūrose. Šviesos diodo darinys su viršutiniu p tipo GaN kontaktiniu sluoksniu buvo pagamintas naudojant supergardelės tarpsluoksnį ir impulsinį auginimą, tokiu būdu gautas toks pats maksimalus VKN kaip ir darinyje be kontaktinio sluoksnio. Tiesinės rekombinacijos koeficientas augo palaipsniui nuo žadinimo intensyvumo dėl krūvininkų delokalizacijos. Pasinaudojus tokia priklausomybe, buvo sėkmingai sumodeliuotas VKN smukimas.
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