Electrical properties and luminescence spectra of light-emitting diodes with modulated doped InGaN/GaN quantum wells

Charge distributions N(z) and electroluminescence spectra of blue and green light-emitting diodes (LEDs) based on InGaN/AlGaN/GaN hetero structures with multiple quantum wells. MQWs were modulated doped by Si donors in GaN barriers, electrons from donors being in InGaN wells. N(z) were determined using dynamical capacitance (C-V) method. Acceptor and donor concentrations near the p-n- junction were approximately N-A greater than or equal to 1.10(19) cm(-3) much greater than N-D greater than or equal to 1.10(18) cm-3. Functions N(z) have periodic maxima and minima; their number was 4 and a period of 10 divided by15 nm, according to the details of growth. The extrema reflect charge distributions in MQWs on the n-side of the junctions with accuracy in z of the order of the Debye length (2-3 nm). An energy diagram of the structures is calculated according these measurements. Shifts of spectral maxima with current (J = 10(-6) - 3.10(-2) A) for these LEDs are comparatively low (3-12 meV for blue LEDs and 20-50 meV for green ones), much less than for previously studied green LEDs (up to 150 meV). This behavior is explained by screening of piezoelectric fields by electrons in the wells. Quantum efficiency versus current is correlated with N(z) distributions and current-voltage characteristics of the LEDs.