A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires

Abstract

We investigated the origin of the high reverse leakage current in light emitting diodes (LEDs) based on (In,Ga)N/GaN nanowire (NW) ensembles grown by molecular beam epitaxy on Si substrates. To this end, capacitance deep level transient spectroscopy (DLTS) and temperature-dependent current-voltage (I-V) measurements were performed on a fully processed NW-LED. The DLTS measurements reveal the presence of two distinct electron traps with high concentrations in the depletion region of the p-i-n junction. These band gap states are located at energies of 570 ± 20 and 840 ± 30 meV below the conduction band minimum. The physical origin of these deep level states is discussed. The temperature-dependent I-V characteristics, acquired between 83 and 403 K, show that different conduction mechanisms cause the observed leakage current. On the basis of all these results, we developed a quantitative physical model for charge transport in the reverse bias regime. By taking into account the mutual interaction of variable range hopping and electron emission from Coulombic trap states, with the latter being described by phononassisted tunnelling and the Poole-Frenkel effect, we can model the experimental I-V curves in the entire range of temperatures with a consistent set of parameters. Our model should be applicable to planar GaN-based LEDs as well. Furthermore, possible approaches to decrease the leakage current in NW-LEDs are proposed. a) M. Musolino and D. van Treeck contributed equally to this work. b) Author to whom correspondence should be addressed. Electronic mail: treeck@pdi-berlin.de dependent current-voltage (I-V) measurements. On the basis of these data, we have developed a quantitative physical model able to describe the experimental I-V curves of NW-LEDs in the reverse bias regime for a wide range of temperatures. The assumptions made in this study should remain valid also for planar devices based on III-N heterostructures, thus making our model applicable also to conventional planar LEDs.The NW-LED structure employed in this work was grown by molecular beam epitaxy (MBE) on an AlN-buffered ndoped Si(111) substrate with the help of self-assembly processes. The active region of the NW-LED consists of four axial (In,Ga)N quantum wells (QWs) with an average In content of approximately 25%, separated by three GaN barriers. The last QW is immediately followed by a Mg-doped (Al,Ga)N electron blocking layer (EBL). The active region is embedded between two doped GaN segments designed such that an n-i-p diode doping profile is created. A schematic Si x O y n-Si(111) FIG. 1. (Color online) Schematic of the employed NW-LED structure. Note that the various dimensions are not to scale.

Extended Electrical and Photonic Characterization of GaN-Based Ultra-Violet MicroLEDs With an ITO Emission Window Layer

“…where Ea is the activation energy, k is Boltzmann's constant, and T is the stage temperature. This type of carrier transportation, as noted in a previous study, is similar to the classical Poole-Frenkel effect, in which an external field is applied to lower a Coulombic well formed by the deep center and in which the carrier can either be thermally activated and emitted or tunneled through this lowered barrier [21,22]. Fig.…”

“…In our devices, we found that leakage current could change markedly with temperature (−55°C to 300°C). Specifically, in the low temperature regime, the VRH current changed slowly with temperature variation, whereas in the high temperature regime (where our measurements were conducted), the current increased rapidly, according to this Arrhenius relation [21,22]…”

“…When a device is reverse biased, leakage current is a highly useful indicator of its internal condition. According to a previous study, possible pathways of conduction fall under two regimes: in the low temperature regime (typically T < 240 K), variable range hopping (VRH) is the major mechanism, whereas in the high temperature regime, thermal activation from the deep centers is the major mechanism [21,22]. The ability for carriers to be thermally or electrically activated depends on temperature.…”

“…The change in potential height can alter the current and electron emission. This relationship can be formalized as follows [21][22][23]:…”

Влияние электрон-фононного взаимодействия и облучения &gamma;-квантами на обратные токи кремниевых фотодиодов

“…Генерация электронов и дырок происходит в области пространственного заряда (ОПЗ) p−n-перехода, где существует достаточно сильное электрическое поле, которое оказывает влияние на величину тока. В большинстве работ, которые исследуют обратные вольт-амперные характеристики полупроводниковых приборов, это явление остается без внимания, а в других влияние приложенного напряжения объясняется эффектом Пула-Френкеля [15,16]. Коэффициент Пула-Френкеля имеет четко определенное теоретическое значение.…”