Tunnel Effects in Luminescence Spectra of InGaN/AlGaN/GaN Light-Emitting Diodes

Abstract

Tunnel effects in luminescence spectra and electrical properties of blue InGaN/AlGaN/GaN LEDs were studied. The tunnel radiation in a spectral region of 2.1–2.4 eV predominates at low currents (J<0.2 mA). The role of tunnel effects grows as the maximum of the main blue line in LEDs is shifted to short wavelengths. The position of the tunnel maximum ћωmax is approximatly proportional to the voltage eU. The spectral band is described by the theory of tunnel radiative recombination. Current-voltage characteristics have a tunnel component at low direct and reverse currents. The distribution of charged impurities was received from dynamic capacitance measurements. There are charged layers at heterointerfaces and adjacent compensated layers in the structures. There is a high electric field in the active layer. The energy diagram is analysed.

The Emission Properties of Light Emitting Diodes using InGaN/AlGaN/GaN Multiple Quantum Wells

“…A dependence of h ω max of the energy eV (V-voltage) is shown in Figure 4. In a comparatively wide range of voltage this function is linear, but the slope of the line is << 1, (in contrast with the tunnel band reported in [3] [4] [5] [6]). Filling of the tail states in the active layer causes this shift.…”

“…We describe the spectra with a model previously applied for fitting the spectra of SQW LEDs [1] [2] [3] [6]. The model implies that an effective radiative recombination takes place when carriers of both signs are injected into the active layer at voltages on the layer U < V. The value of U is close to ϕ k .…”

“…A model of radiative recombination in 2D-structures with band tails caused by potential fluctuations was successfully applied to luminescence spectra of LEDs with single quantum wells (SQW) [1] [2] [3] [4] [5] and radiative recombination by tunneling was detected at low currents [3] [4] [5] [6] [7] [8].…”

Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells

“…3 (see a method of measurements in [8]). The LEDs with MQWs have wider space charge width than ones with SQWs [2][3][4][5]7]; in both cases the width for green LEDs is wider than for blue ones. This fact corresponds to a low probability of tunnel effects in the LEDs with MQWs.…”

“…Low currents could be understood as a tunnel component; tunnel currents in these LEDs play some role at J 3-4 orders of magnitude lower than that for SQWbased LEDs [2][3][4][5]7]; J(V) curves of SQW-based LEDs differed from MQW-based LEDs because of a wider active layer [1]. A good approximation of the J(V) curves for MQW LEDs was done when not only a series resistance R s at the linear part at higher J was taken into account, but also the quadratic part: J ( V-V 1 )…”