Do you mean the sleep/wake/lock button on the side of the device? OR the home button on the face of the device? In any event IF any of your button are broken you can get an onscreen button to use to replace the function using accessibility options on the iPad settings. Settings/General/Accessibility/Assistive Touch
The only button that brings up the home screen and icons is the home button located at the bottom of the screen in the center. If you have a passcode enabled, you will need to enter that.