Resonant tunnelling diodes (RTDs) are pioneering quantum mechanical phenomenon-based devices that produce unique current–voltage (I-V) characteristics. Here, the impact of design parameters on I-V characteristics of AlxGa1-xAs-based asymmetric double and triple barrier RTD structures have been investigated and compared with their corresponding symmetrical configurations using the Nanohub tool. The discrete energy states, wave functions probability, and I-V relationship of RTD are explored using the non-equilibrium Green’s function (NEGF). Applying an external voltage to the symmetric double barrier RTD (DB-RTD) with Lb1 = Lb2 = 3 nm, produces a peak current density (Jp) of 0.49 MA/cm2 with a maximum negative differential resistance (NDR) region of 3.5. Further, when we increase Lb1 from 3 to 5 nm keeping Lb2 constant, which seems asymmetry DB-RTD, the Jp decreases and occurs at lower voltages. However, when we change the width of Lb2 from 3 to 5 nm keeping Lb1 constant, Jp decreases and occurs at higher applied voltages. In addition, we investigate the I-V nature of asymmetric triple barrier RTD (TB-RTD) for different third barrier widths (Lb3), which vary from 3 to 7 nm, keeping Lb1 = Lb2 = 3 nm. It can be noted that there is always a drop in Jp1 and a hike of Jp2 for each increase in Lb3. The characteristics of the NDR region can be tuned in a broad range by manipulating the asymmetry TB-RTD structures to get the desired device performance.